Iirc the database manager uses your local connection, while the database connections uses the server connection (providing the site is uploaded, I guess?).
The issue is that you likely do not have your MySQL server set to accept remote connections, thus you can only connect locally from the machine hosting the MySQL server.
To complement, if this is the problem, it can be worked around by using SSH tunneling ("Over SSH" on Wappler) if the hosting provider provides with SSH access