Map Network Drive : Issue(s)

We have 2 small PC based Windows 11 servers used for Business Files, Music, Photos etc. Running Win 11 25H2 managed via a Workgroup with shared folders - ( c drive)

We have 2 Lenovo Thinkpad T490s machines running Windows 11 25H2 with successfully Mapped Network drives on the 2 PC/Servers, again in the same Workgroup and using the User Name & Password credentials of the individual PC/servers.  These were Windows 10 builds upgraded to Win 11.  The mapped drives would have been activated under Win 10.

We have recently purchased 2 new Lenovo Thinkpad laptops also both running Windows 11 25H2 and these also have been added to the same Workgroup.

These use MS Workgroup accounts with Pin login.

We have attempted to Map Network drives from the new Laptops using the login credentials of the 2 PC/servers ( User Name & Password) and receive  the following error:

"The mapped network drive could not be created because the following error occurred:

We can't sign you in with this credential because your domain isn't available.  Make sure your device is connected to your organization's network and try again"

Any thoughts on how to resolve.  This is becoming a real frustration.   

Murray