Register Failed: No Response From Server

Continuing the discussion from How to access freepbx outside your network:

I’m using NO-IP and am getting the following error on Zoiper, and my Obi Hai Register Failed: No Response From Server It seems to work initially, but starts failing registration within 5 minutes, then I can’t get it to register again. I’m able to get the zoiper app on my android to register, and on my desktop, but am having this issue with obihai, and also other remote zoipers for other staff. Any thoughts or help in troubleshooting would be appreciated.