This error usually means your computer cannot connect to your organisation's SQL server. You will need your IT team to investigate, but the following checks will help them narrow down the cause:
Check whether the error affects only you or all users.
If all users are affected, the problem is likely with the SQL server.
If only you are affected, check the ODBC connection on your machine. See Set up a new ODBC link.
When referring this to your IT team, explain that the Dimensions error is a symptom of a connectivity issue between your computer and the server. Common causes include:
Network issues.
Domain Name Server (DNS) issues.
Issues with the services on the SQL server.
If an alternative server is available, you can back up the database, restore it to the alternative server, and configure Dimensions to connect to it. This is not ideal if the alternative server is less capable, but it may restore access to Dimensions while the original server is being fixed.