Windows 7 pro shares stop working for some windows clients

Windows 7 pro PC windows file sharing stops being accessed from certain windows 10 and windows 7 pcs

We have a PC that has windows sharing enabled with several directories shared.

This configuration has been working for the last 3 years.

This morning 1 windows 7 pro and 2 windows 10 computers can no longer access the shared folders.
1 windows 7 pro and 2 windows 10 PCs can access the shares in the same way as always without problems.

I even tried with my laptop not from this environment to access the shares and it won''t work (my laptop is windows 10).

Not sure where to start.
All firewalls off on the local network.
Network adaptors are set to private on the windows 10 and work on the windows 7 pro PCs.

No anti-virus software is present.

Any help or utilities to check or verify settings would be helpful.

I have rebooted the router.

pinging the name of the window 7 pro with shares resolves in the proper IP address.
Browsing and trying to use the share by IP address gives the same result.

Thanks,
Gilbert.