Hi @Daniel Hargrove ,
SQL Server does not exist or access denied
About this issue, Some of the problems from the server end are as below:
Installation of the SQL server is not done in the computer that is specified in the connection string.
SQL Server is not started.
The SQL Server name is different from the name of the computer.
The database is offline.
Renaming of database files.
The database is moved to a new server.
And some of the problems from the client end are as below:
In-existence of the name of the computer on the SQL Server
Ensure to specify the correct occurrence name if you are trying to access a named occurrence of SQL Server.
Using incorrect protocol.
The presence of any cluster in SQL Server may lead the network adapters to get configured incorrectly or might have an incorrect name.
It might just be the side effect of an MDAC mismatch.
Details: https://bobcares.com/blog/sql-server-does-not-exist-or-access-denied/
If the firewall on the server is blocking any incoming connections then check the firewall settings for the server operating system. However, in case if it is enabled then verify the port number the SQL Server is using is open in the firewall. Also, verify the UDP port 1434(if you are using dynamic ports).
please follow this link to see if it helps: https://www.sqlserverlogexplorer.com/database-does-not-exist-access-denied/#:~:text=Sometimes%20%E2%80%9CSQL%20Server%20does%20not%20exist%20or%20access,port%20exception%20is%20also%20added%20to%20the%20firewall.
Verify that the SQL Server service is started and ensure that the database is attached and online. Also, verify that the SQL Server Browser service is started on the application server if using a dynamic port for SQL Server.
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