Moved your post to the thread that was at the top of the list so we don’t have two of the same.
The forum is entirely run by volunteers so we ask people to use the forum search to see if something has been answered already - or multiple times.
In this case, something, somehow, has got in to the database that the web front end can’t cope with. The simplest solution, given there is no SLA or support for the free service, is to use the CLI tool to delete the devices and re-enter them from either the CLI (preferable) or via the web console which works 99% of the time for me, but just occasionally I manage to confuse the browser enough that I break it all. That said, the CLI is more of an atomic commit to the database, so if I’m doing a fair number of devices I use that.
Sometimes editing a setting can cause this issue.
If I get any form of detail (both EUIs) that can help the TTI developers trace such situations I do pass it on.