HELP! Please. "You do not have permission to save files to this location."

Just to clarify, your Macs work, but Win 10 not?
And xls can be saved, xlsx not?
Your description confuses me a bit.
What is working where, what not?
What is the target? A file share? 

- But in general, if you can write one format, but not the other, it doesn't have to do with permissions.
- UAC (Windows) may play a role (some system folders you can only write with administrative permission, even you are admin), but would not explain, why one format works, the other not.
- Excel has some settings to avoid opening or saving old formats. You can set them in the Options - security center - .
The settings are a bit confusion, everything what is checked there is denied.
- Last but not least, Virus scanners sometime develop their own live, just a point top check.

thanks - clarifications:

Just to clarify, your Macs work, but Win 10 not?
No the opposite, MACS do not save xlsx, Win 10 does

And xls can be saved, xlsx not?
YES
Your description confuses me a bit.
Sorry
What is working where, what not?
No save as on macs, yes save, no save as. Only xlsx is problem

What is the target? A file share?
No, local disks, external such as one drive DOES save.

no virus scanners running

Can you save the files in other locations?  Did you check the system preferences  privacy settings to see if your Excel can save to the locations?

On each mac I cannot "save as" xlsx to the local hard disk.
I can save to off disk locations like one drive.

I have recently been trying an addin that turns out works only on Windows.
Also been running VBA snippets.
I will re test a few locations again now

MacBookAir
dropbox local - no
icloud drive local - no
onedrive cloud - YES

Just tried on Mac Mini
No xlsx save on local disk
When trying save to onedrive cloud I was required to "Grant access", whihc then worked when i followed the links

So, it looks like a MacOS problem, right?
At least windows maintains a list of "trusted" file locations.
But this would not explain why XLS works and XLSX not.

You talked about VBA snippets.
XLSX can not have macros, you have to save it as XLSM.
Maybe this is the issue?

No xlsm is neo issue as vba is disabled
I suspec Office 365 because it is across all macs, not just one and no problem on Windows 10 but I cannot find a setting, despite having a message on one occasion on one mac saying I did not have permission from the admin (who is myself) to edit on macs

where is the list of trusted file locations?

ok found that.

So, three Mac s'Excel won't save xlsx files to Mac local disks. 

I think this is a setting or policy set in 365 Admin online, or in Windows 10 that propagates, because each time I reinstall on Mac I see "privacy settigs" being downloaded from the cloud.

Any help here? 

Ok so reinstalled office on all three macs. The first two I noticed a privacy settings download being applied when starting up. So for mac 3 I copied the installer from one of the others, disconnected from the internet and ran the install, had to allo an auto update, but disconnected again before that could do anythong else.

Now "save as " XLSX works. I am sure now this is an Office Admin Online settigns matter.

The trusted file location is
File - Options - Trust Center - Trust Center Settings - Trusted locations.

Thanks, yes found it, no such thing on Mac.

At least under Windows Excel. Possibly Preferences on MacOS

Nothing there.

Does three Macs mean all of your Macs?

Yes. 

Or do you have a working mac? Just to compare the settings?

No. 

Are you in a corporate network? It ist possible, that you IT-Staff defined some Settings?

No, I am the Admin.

Have you checked Security and Privacy? Under privacy you can set Access Permissions for Applications.

Yes, will look again though.

Have you checked Word in docx format?

Yes, works ok.

Have you tried to start the Mac in save mode?

Safe mode. Not yet.

Have you checked with a different user (clean profile)?

Yes. Good question.

At least make sure for testing, that the file name doesn't contain special characters.

It doesn't. Tried all sorrts of files and names.

As you are member in the Office Insider program,

Yes.

can it be connected to an update?

I've installed several times and now got one working. This time there was no "downloading settings" notice so pretty sure that is/was the issue. Still not found where tehse are set. 

Has it worked before and when the issue was starting?

Oh yes worked for years. Started two or three days ago, noticed today.

Is your system Up to Date (MacOS as well as office)?

Yes.

Thanks for sticking with me, appreciate it.

Anthony

OK, you may have a look if any related update was installed before you recognized the issue.
Insider preview comes weekly, because they fix a lot of bugs as well as they create new ones.

If you have a working MAC now, you may now be able to compare the MAC OS security settings as well as the Excel settings. This looks like, that there is an administrative setting, which either affects the Mac in general or what affects Excel.

I don't think that Microsoft involves into MacOS settings, but possible that changes from one site involves into this issue.
Either Microsoft changed a default setting what is not correctly interpeted by the MacOS, or Apple changed something what is not yet implemented into Office for Mac.
Nevertheless, following your decription would lead me to the idea, that there is a central managed administrative setting, which actively changes a default setting.

So, its time now to walk through all settings on the Microsoft Online side.
Keep in mind that not everything, what works for MS clients may not work in the same way on Mac OS. Means the realisation on Mac may be different from Microsoft. And this my result into side effects (seen this a lot of times in the past with Apple devices). 
If nothing helps, make sceen shots, revert everything to default an then enable one by one to see, which setting results into the issue.    

well understood!
My key thought is this:
While my Macs auto update asap, one of them wasn't updated yet,
add to this, that Macs don't share their settings of this sort between each other. Sure they are all about permissions, but not to this level of granularity, an MS file type.
On the other hand 365 does have central policy control and it's instant, and it is only the one file type xlzx and NOT xls etc. So that really feels like an MS matter.

I've just been through the trust center yet again.. perplexed why on my last MBA (mac laptop) there was no "settings download" and then file save as xlsx worked.. in fact I'll just check this is still the case..back in a sec  

right the, MBA saves XLSX ok now.
MPro does not, still says no permission at location
Mini is redownloading to reinstall

It is conceivable that careful deletion of Mac settings files may make the difference.
However, those downloaded settings updates seem to me to possibly be the source of the trouble because I have never seen these before.

I have looked and looked through Windows security and privacy and Windows Excel and just can't see anything that remotely looks like "don't allow save as xlsx"

So you mentioned compare sttings.
That suggests comparing the above mentioned carefully deleted settings files before trying to fix the MPro.

What the one currently downloading to reinstall will do I dare not contemplate.

Do I think it's a screw up by Apple or MS? No, doesn't feel like it. Feels like an admin policy setting.

But hey, just a feeling.

so, reinstalled the MPro second time, first time reverted to current channel, this time switched it to beta channel, tested before beta channel updates were applied and saved as xlsx ok .. not sure I believe it

feels like something somewhere has been fixed. There was something about "experiences" that I unticked, having recalled ticking it very recently.. shirley not that.. this was a tick box in Windows Excel options.

Finding any settings that appear even remotely relevant is the problem, on both mac and pc

I think all three Macs are now working for "save as" as xlsx (from existing xlsx), after reinstalling in some cases twice.

Not really clear why.

There was a tick box about "experiences" in the Winodws Excel option settings which I unticked after recalling I ticjked it very recently. But don't really think that was it.

Anthony