Could you please specify which element deletions caused this issue? It would also be helpful if you could provide a screenshot for reference.
Apologies, I wasn't clear enough. I am referring to the Dynamic Content elements. I created a collection, and within that collection, I added several items. When I try to delete these items completely, I receive the error shown in the screenshot.

Additionally, the username and password you provided are not working—perhaps they haven't been activated yet?
Apologies, the user was not activated. It should be working now.