If the application stopped connecting to the PC, then it means there is a problem with the database. Since it's using Access to store the information, I would like to recommend that you check if the Access database engine works. To do this, go to Start > Run > services.msc and locate the Access engine in the list. Restart it, then restart the computer and initiate a new connection. This time it should be able to connect successfully. In the connection window of the application, check the username and password.
