If the software is unable to connect, it may be caused by the SQL instance not running. This can happen when the Windows start up process does not start the SQL instance.
To check the instance:
1. Open SQL Server Configuration Manager (this can be searched from the Windows Start Menu)
2. Find your instance name in the browser window. If the instance is running, the 'state' will be 'running', else the 'state' will be 'stopped':
3. If your instance has stopped, it can be started by right-clicking the instance and selecting 'start'