During my meeting, visitors were kicked out of the board, we had to use Paint…

I was holding a course for 12 external participants, and was planning to use Miro. It worked fine until I broke them into groups, and told them to make a diagram each. Soon after they started complaining that they were being kicked out. I tested myself in a private browser, and the tab where I opened Miro closed itself (“I got kicked out”).

I did not have the time to troubleshoot in detail, or to get too many details from the participants. After the course was over, I am able to log in just fine in my private browser. During the course, there was always one or two visitors logged in, but not all at the same time.

I told them it was probably due to too many people logging in at the same time, but have no idea if that is correct or not. Each group had to use Paint or other substitutes, and share screen afterwards, which was a bummer.

Anyone know anything more, or have experienced anything similar?
Enterprise subscription (I presume), with a public link to the board.