The error itself describes nothing related as it is a common error. there will be scenarios where the SharePoint farms that you are planning to migrate having bunch of custmizations and third-party integrations. this is one example i’ve been facing recently.
The Site was migrated using DB attached method and whatever the Custom Solutions were sitting on the source farm wrere migrated to destination (2013) Farm too. there were many Web applications and many of them worked perfectly but not this one.
Prompts “Sorry Something went wrong, An Unexpected Error Occurred” when accessing the destination site URL.
ULS Log is the god at this point.
Searching ULS through this correlation ID won’t give you the exact point here. Instead search through URL. At this point the error was occurred due to the Nintex Workflow Solution which is a third party WSP deployed and not configured. Retracting the two WSPs related to Nintex from this particular web Application resolved the error.
This is the ultimate reason behind this error. This Home page has been using a Task list associated to a third-Party Solution. Web Part remains fulty unless the connection and licensing configured properly.
Wrap-up: Any Cutom Solution used (only the ones used within your target Web application) in the Source Farm has to be deployed to the Destination farm. not only deployed and enabled but conigured for Connections and Licensing. in above scenario, the third-party solution was not licensed and neither configured as required which cuased the error in destination.