activate windows 8.1 Connected - or upgrade using what ISO?

You can call Microsoft Support to determine why you cannot activate. I have not heard of a Key going bad on a legitimate build.

If you have 35 GB of free space, you can upgrade to Windows 10.

https://www.microsoft.com/en-us/software-download/windows10

You would need to activate (pay) during installation.

i did call Microsoft activation support and they said to call Toshiba.....toshiba support was useless.  the product is out of warranty.  these tablets have imbedded windows.....12.6GB free of 25GB total......there has to be some special way to upgrade this

Well....think you are asking the wrong question at the wrong place.

it appears that you are trying to use a third party program to generate an unlicensed key.

why not just contact Toshiba support...need serial numbers, and ask them for help

here's the link for that model:
https://support.toshiba.com/support/family?fname=Encore%202

what did I say that gives you the idea I am trying to generate an unlicensed key by a third party program?

actually, I see that the program is a key finder for existing keys on the device.
https://www.magicaljellybean.com/keyfinder/

if you found the correct key,  and Microsoft will not activate it,  the you have to upgrade.

Just contact Micro$oft and ask them the best upgrade path for that device. I mean if they are going to tell you that the keys have been used too many times. then ask them what your choices are.

the device is not that expensive so make sure you compare this cost with the cost of just getting another device.

There is not enough space to upgrade and if Toshiba will not help with activation, there is not much you can do

correct - I used magicaljellybean to generate the picture that was originally attached to this question to show the key and windows version.

(I tired to support an iPad once like this - the devices seemingly become bricked with these minor hiccups).  crazy.

the question again:  does anyone know if there is an upgrade path for this device I can take?  how do you upgrade an imbedded OS?   or, if I wanted to purchase a key - for what version of windows would I get a key?......... or seemingly just throw these devices that currently work fine out?

There is not enough space to upgrade, so that is out of the question.

 if I wanted to purchase a key - for what version of windows would I get a key?

You would need to purchase a Windows 8.1 key and I do not think you can do this. One source of old software is eBay.  Make sure you get a legitimate vendor.

The key posted in your screenshot is not correct for activation of "Win 8.1 Connected SL", it's only to allow installation of the (non-European "N") Windows 8.1 with Bing media.

If you Google the key you'll realise why Microsoft don't allow it to be used for online activation.

In your question you state that the embedded keys don't work - have you extracted them?  They are not the same as the key JellyBean is displaying in the picture.  If you're not sure then you can use this tool to extract the embedded key for each tablet
https://neosmart.net/OemKey/  (You don't need to put a real email address in the download box to get the download)

I'm guessing Microsoft are complaining that you're trying to use the 6NDQM key to activate.  If you want Windows to activate using an embedded key when you're upgrading DON'T enter a key when you are asked.  Windows installer will then look for the embedded key.  If it doesn't find one it will prompt you for activation after the OS is installed.

Which OS was supplied originally with the tablets?

MASQ:  OK, the new key is PRP4N-XYXYX-63QT4-9GHW3-7T8JQ   ...this key wouldn't verify when entered either

Windows 8.1 with Bing version 9600

see attached screenshot
Screenshot--3-.png

No embedded keys don't work if you enter them manually - only retail and VL keys work like that, you have to let the OS installation recognize them and not enter anything at the prompt.

I've edited your valid embedded key so it can't be copied for use in the future (they can be "injected" into hardware).

It looks like the OEM flag at least has been recognised though as the Tosh logo is displayed.

Did the tablets suddenly become spontaneously unactivated or have they been unactivated since you have had them?
Trying to understand why your OEM activation has been lost, which should help in fixing it.
If you've had them since new from Toshiba do you have the recover DVD that went with them?

If not, you can generate an iso here
https://www.microsoft.com/en-us/software-download/windows8ISO
Make sure you get the CoreConnected with Bing SL version (32bit 8.1 SL)

the tablets were activated - and according to the manager in the department that uses these tablets, one day the activation wizard just popped up on all three tablets.

these 3 tablets were purchased from Toshiba refurbished.

i don't believe any of the packaging materials were saved with the tablets, including any dvd's.....