Unable to get to the top level folder on my iPad andiPhone

I can open Mindjet Maps on my iPhone and iPad and interact with the last map opened.

When I press the folder icon it attempts to connect to my DropBox Files folder but fails. On the iPhone I can generate the error message "cannot open folder unknown error".

If I add a new map and choose Location, I can see the folders in my Dropbox files and add a new map!

What's going on?