They'll let you register darn near anything from what I can tell. I've had some issues trying to register some stuff, a polycom IP phone comes to mind. I also was having trouble getting Zoiper to register to them, I know it can be done, I'm just a real noob at voip stuff. I'm sure I had something set wrong. I'm trying to teach myself something new. Voip.ms is cheap, which makes it good to use for learning. I've managed to get a dozen or so things working with them. I think my issue is the "hospitality solution" in place at this hotel. This particular ATA registers and works just fine at home. This place has switched to some "Allbridge-One Connected Experience" product that is just annoying. I'm using my own router, plugged into the lan jack behind the desk, but even that runs through this ridiculous service. I have to "re-up" every so often because it shuts you out after a certain length of time. I stayed here last year and none of this nonsense was here. I plugged in, and I was off and running. Everything worked just fine. One interesting thing I've noticed, when I'm on the guest wifi, certain apps and things won't work right on my phone, social media things and whatnot, but when I'm connected to my own little private wifi I set up, they work just fine. My guess is they block out or throttle certain things. Voip is probably one of them.