If you are receiving the "cannot connect to database" error message on the machine/server where the database is held (server), there are a few things that need to be checked before proceeding.
Firstly, we would always recommend re-starting the machine/server that holds the database and trying to access TaxCalc after a restart. If this works, you may want to check whether the Postgres service is set to delayed as per our article for Postgres does not always start when the "server" machine is rebooted.
In order for TaxCalc to work, we require two windows services to be started.
Usually the above troubleshooting resolves the application not working. If TaxCalc still does not work, are you able to check if there are any other applications that you are also experiencing difficulties with? If so, this may indicate that there are other issues that need to be addressed and we would recommend contacting your IT team accordingly. Please note TaxCalc will not be able to assist you with this.
If TaxCalc is now operational on the server but you continue to have issues connecting from the client machines please see our article for Cannot connect to DB - Client machine