Quick update: I used the T-Mobile additional line free offer that started today (March 1, 2017) and inserted the active SIM card in iPad. I no more have this issue.
Can someone else that is just having an iPad (without a SIM slot) test DIGITS app and confirm if the incoming call screen stays there when the line is picked up in the primary device or some other device? If that's the case, T-Mobile may still have to look into this defect and fix it.
You missed telling us that step that you didn't have a SIM in the previous iPad so that it was on WiFi only. I'll have the team look at that again, but it's likely that the device isn't waking for the push notification since it's coming in via WiFi. I know we're updating some items in that realm, so will make sure the team is taking another look at that particular combination.
Thanks for the update!
This thread was the product of our fantastic collaborators during DIGITS Beta! As many terms have changed and bugs have been exterminated since the Beta launched, the information here may no longer be accurate. If you still have a question, please search our active threads or ask a new question in the DIGITS space!