Unable to start update campaign in Device Management Portal


I'm getting started with the Device Management Portal and I've started and stopped a few update campaigns, and deleted them afterwards, all without any problem.

However, I've now tried once more to create an update campaign but this time it always fails to start with the message "Active campaign already exists", even though there are no other active campaigns. In fact, this is the only campaign present.

The behaviour is actually identical to this forum post from a few months ago: https://forums.mbed.com/t/update-campaign-stop/8366

Will my account need some sort of recovery process as suggested in that forum post?