Cannot Reinstall Connector

My WS2012E server and four clients were working fine until my 18 month old granddaughter walked into my office and pushed the server's reset button. (She probably wanted to see the lights blink like her other toys!). After the server rebooted, the client backups stopped. I was able to restart the automatic client backups on three clients by disabling and then setting up the backups. However this did not work on the fourth client. When a backup started on the fourth client, I got a message saying the client was not connected to the server in spite of being able to access the shared folders.

I then uninstalled the windows connector and reboot the computer. When I then tried to log on as the user (not system administrator), I got the following message: "The security database on the server does not have a computer account for this workstation trust relationship". However, I can log on to the network using one of the other three computers with the same account name and password.

I can also log on to the fourth client using the system admin account. When I then try to reinstall the
connector using the user (not system admin) account, I am told the computer is "already connected to another Windows Server network and have to remove it from the current network". What's happening? Thanks in advance.

BTW, I've installed a plexiglass shield over the server's front panel!

Thanks, Bob