Jordi: it's a pool of servers and your account is locked to 1 specific one. (or it used to be like that) so it could be that those others work fine.
It sounds reasonable. My thought was that traffic was dynamically redirected to one or another server, based on load balance, maintenance, or any other criteria, but simply don't know it.
However it is made, and regardless if it only affects some or all of the users, the service MTTR is way larger than what I would consider "reasonable" for a professional service. I have been needing it badly since today at 14:00h and simply can't use it yet.
I am a big fan of B4X in general and I'm really happy with what we get for the prize with B4A and B4I, but this is not the case for the hosted builder service.