We have a shared NAS device (Seagate Blackarmour 440) which we store our Archived jobs on and is shared to Windows and Mac workstations. They connect using SMB.
We had to power off the NAS drive for a day while some electrical work was carried out and when we powered it back on all the windows users worked fine however 3 our of the 4 macs failed to connect.
When connecting we tried CIFS and SMB but neither worked.
Here is a summary of which ones could and couldn't connect:
IMAC 10.6.8 x 2 - Could not connect
IMAC 10.8.5 - Could not connect
IMAC 10.9.5 - Connected fine
It was strange that is worked before for over a year and now is refusing to connect.
I have added a screenshot of the message we are seeing.
I am a windows user mostly but have had to learn MAC os as we have them here. I am not a expert but get by quite well.