Errors connecting to NAS - Windows 11

[aallenmapc]

We are running our NAS on a TS-453A (FIRMWARE: QTS 5.0.1.2173 Build 20221001) and having issues adding new users who can access their NAS folders via file manager and so we can set up daily backups etc. using Macrium Reflect. The User accounts have been created are running Windows 11 - but we are getting the following error: 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. If you previously signed in on this device with another credential, you can sign in with that credential. Any help would be greatly appreciated.

[dolbyman]

Well are you adding user/group rights via LDAP sync ?

Some screenshots would help