It sounds like you are experiencing an issue with your MongoDB connection. There are a few possible reasons why this might happen:
The MongoDB server may not be running. Make sure that the MongoDB server is running and is reachable from your application.
The connection string you are using may be incorrect or incomplete. Double-check the connection string to make sure it is correct and contains all the necessary information.
There may be a network issue that is preventing the connection from being established. Check to see if there are any issues with your network or firewall that might be blocking the connection.
There may be a problem with the MongoDB driver or library you are using. Make sure you are using the latest version of the driver or library and try upgrading if necessary.
To troubleshoot this issue further, you may want to try connecting to the MongoDB server using a tool like the MongoDB shell to see if you can establish a connection that way. This can help you identify whether the issue is with your application or with the MongoDB server itself.