iOS tester invite can't be completed

Hi everyone,

Posting this here because I don't know if this is a regular issue with Median. I've invited a number of testers but each of them has not been able to finish the registration process for iOS testing through Median's system.

Every time we attempt to register a test device, we go through all required steps just to find the "Register Device" button doesn't work.

All steps have been followed in line with the instructions, and both fields are displaying as valid.

I'm on a time crunch to get one of our apps shipped, so any help would be much appreciated.