Hi @Danielle A Kennedy ,
Welcome to Microsoft Q&A!
Which version of Visual Studio are you using?
Is it a remote server? Please check if the firewall is blocking the connection on the remote machine.
You can try to add a connection in Server Explorer and test if the connection succeeds.
Besides, please check if the SQL Service instance is running, from SQL Server Configuration Manager or using the following command:
sc query mssql$instancename
Sincerely,
Anna
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