1. Check whether the user account is active and has the appropriate privileges for the network share.

2. Check the credentials for the user account on the Domain server, that they are correctly set and any passwords are still valid.

3. Check that the network share is defined correctly on the Domain server, with permissions set to allow access for the specific group of users.

4. Check that the user’s client system is configured with correct domain name, username and password, for accessing the Domain server.

5. Check the status of the domain server for any errors or issues that could be causing authentication issues.