Same problem and I'm shocked!
A couple of years ago, I bourght a iRig HD and had the same problem. I opened a support ticket and got some hints how to solve it (restore In-app Purchases etc). After all I got the situation, that sometimes Amplitube could login but after a restart the connection was temporarely lost. After all it was too much hassle for me and i send it back to the shop.
Now, four years later, I want to give the iRig HD 2 a new chance - I like the specs and the fact that it's not longer bound to Apples world
.
It's in use now for three month. Use it on my Windows 10 laptop with Studio One and my new iPad (2018 9,7 Zoll, Wi‑Fi, 32 GB) with Loopy HD, Audiobus, Garageband, AmpKit without any issues.
Today I wanted to do the registration to get AmpliTube on my iPad..... and after some hours reading instructions, creating my account, doing registrations I run into the same problem
Seems to be i'm a complete idiot.
With regards