Hello @Andrew_Lockwood, it would be awesome if you could test with one of their iPads and see if you can get things working!
I spoke to my team about this issue also, and it looks like we had some issues with Android devices a while ago which seemed to be solved by users entering 255.255.255.255 into the app once it times out and you are able to enter an IP. This would be a good test to try too! Let me know what happens.