Dataset Error: Failed to open a connection to the database – Synonym error

Dataset has been in production use for a long time. I use EF a lot now, but these still need maintenance and modifications for user requests. Error message was:

Wizard form
An unexpected error has occurred.
Error Message: Failed to open a connection to the database
Check the connection and network state and try again

This was on a remote server so I thought there may be a timeout issue. However a search and thanks to:

https://social.msdn.microsoft.com/Forums/en-US/33575eae-24bd-470b-b93e-2083af49cfe8/unable-to-add-new-query-in-tableadapter-query-configuration-wizard?forum=adodotnetdataset

revealed that there may be a bad synonym in the database. The writer of that post used Activity Monitor, but SQL Profiler might also find that there was a wait resource of ExternalResource.

Although I did not check the Activity Monitor, I did check my synonyms and they were pointing at an old server. Repaired them to point at a correct location and the dataset issue has gone.

Solved.