Answer:

1. Check whether the operator exists and whether he has logged into the wrong account set.

2. Is the SQL server running?

3. Check whether the database is not installed after reinstalling the system, or the database is not attached after installation.

4. On the server Startnet page, in the system settings, click on SQL server parameter settings, and then click on test connection to see if the test is successful. If the test is unsuccessful, check whether the SQL server name (or IP) is consistent with the name of the SQL service manager. If they are inconsistent, change the server name (or IP) to the name of the SQL service manager.

5. Try to reinstall the client. The user number must be the same as the user number on the network server. (It is possible that the user number of the client is different from the user number of the network server).