Steps to reproduce

1. Login as admin.
2. Go to "Site administration > Activity modules > Manage activities".
3. Enable BigBlueButton using the icon in the Enabled column.
4. Create a course.
5. Enable edit mode.
6. Open the activity chooser and select "BigBlueButton".

Expected behaviour

The form to create a BBB activity is opened.

Current behaviour

The error "No response returned for call" is displayed:

Or, when debug is disabled:

Looking at this issue with the UX team, we agreed that the problem is that from Moodle 4.4 onwards, admins are not getting a warning when they enable the plugin and no BBB URL is defined. The workflow should be reviewed to show a warning, similar to what we had in Moodle 4.3, to warn admins about the URL empty, and probably disabling the BBB plugin until a valid URL is defined: