Teachers often want to send messages to students prior to the start of the term, while the course is still hidden. In certain cases this fails with a very unhelpful error message: "webservice/formatnotsupported".

The problem occurs when there are more than 20 users in the course and all are selected. Bulk messaging fewer users in a hidden course works as expected. Bulk messaging all users in a visible course works as expected.

We're running 3.7.1+ (Build: 20190801). I'm also able to reproduce the issue on demo.moodle.net.

To reproduce:

• As a teacher, log into a hidden course with more than 20 users.
• Open the side menu and go to the Participants page.
• At the bottom, click the "Select all <n> users" button.
• Choose "Send a message".
• Enter some text in the message popup and select the "Send message..." button.

Workaround:

Send the message to one page of users at a time.

To replicate:

Case 1, in which the current user is selected (enable dev mode first to see the full exception message):

• As a teacher, log in to a hidden course with a few students enrolled.
• Go to participants and select yourself and one other student
• At the bottom of the page, using the 'With selected users' select menu, choose 'Send a message'
• Enter a message and click send.
• Notice the exception as per the attached screenshot

Case 2, in which the current user is NOT selected:

• As a teacher, log in to a hidden course with a few students enrolled.
• Go to participants and select a student
• At the bottom of the page, using the 'With selected users' select menu, choose 'Send a message'
• Enter a message and click send.
• Notice the notification saying '1 message was sent' (you might need to scroll up)
• Log in as the student you just sent the message to
• Notice you don't see any message in messaging.

Workaround:

None.