Question Connecting to computer on same network fails

Oct 27, 2020
Good day to you in your favourite timezone,

I've been fighting with a - most probably - minor thing that I simply don't understand. I guess I've already pulled out half of my greying hair, these past few days.

Given: my home network and 4 completely identical desktop PC's made by Dell bought off a liquidation. All in good shape, I5, 8GB RAM, 120GB SSD for Windows, named WS1, WS2, PRINTSERVER and NASSERVER.

PRINTSERVER hosts a colour laser multifunctional and an A3 Epson inkjet printer.
NASSERVER has, in addition to the 120GB bootdisk 2x2TB 2.5 SATA HDD.
WS1 and WS2 are two desktop workstations me and my wife are working while @home during Covid.

All four PC's have the same official (fresh) Win10 Pro installed from the original DVD and SMBv1 is enabled on all four. Local user names and passwords are the same on all four. File and printer sharing enabled on all four. All Windows updates done.

Now comes the thing.

Command \\NASSERVER executed on WS1 and WS2. Both asking for a username and password. Entering username and password, success, the two shared disks come up. Mission accomplished.

Command \\PRINTSERVER executed on WS1. Asking for a username and password. Entering username and password, success, the two shared printers come up. Rightclick, install, OK to both printers on WS1. Mission accomplished.

However, the same exact thing fails not-so-spectacularly on WS2. After entering the username and password Windows Security complains that "The user name or password is incorrect" for user admin and gives another prompt to enter the password.

I retried it at least 20 times to no avail. I tried to create a connection on this WS2 to PRINTSERVER using the Credentials manager by manually entering the user/password combo, also unsuccessful. Tried to reboot, tried to flush the ARP cache and let the PC soak an hour. Tried to create the same connection to the IP address of PRINTSERVER, also unsuccessful, same error message.

It MUST be something with local usernames, although I made sure I use the same local username and password on all four PC. And, it works for NASSERVER on WS1 AND WS2, so it SHOULD work for PRINTSERVER as well.

Icing on the cake: RDP connection from both WS1 and WS2 to both NASSERVER and PRINTSERVER work perfectly with these credentials....