Unexpected error: An item with the same key has already been added.

I'm using Excel v 1711 which has the ability to connect to a mysql database.

When I log in to the database, I see a list of my tables, which is great. But when I highlight any table, I get "Unexpected error: An item with the same key has already been added."

The only solutions I've tried so far are

(a) to create a new workbook and go through the same steps. But that does not solve the problem.
(b) to open the queries and connections to see if there were already any other such connections I had tried in the past. But nothing was there.

I've googled the error but didn't see any posts involving Excel.

The mysql database is hosted at AWS.

Any advice? Thanks.

Solved. User Error!