Thank you for your post.
Primarily, there are two common reasons for this error. Firstly, you should check if the iTWO costX Database service is running. Open your Services windows and scroll down to “CostX Database” and check the Status. If it is not running, right click and select “Start”.
If you have done this and still get the unable to connect to the database error, then this may be due to a firewall or antivirus software assuming that iTWO costX is a malware. In this case, you will need to either add the Exactal program folder to the AV exclusions list of disable the AV scan and run iTWO costX installer again to repair iTWO costX services.
Hope this helps!
iTWO costX Forum Admin