I am adding a small feature to an existing app which fires a user notification when a user enters a predefined geo-fences. When I load the same app on my colleagues' iPhone 6S (2 have a 6S) and an iPhone 7Plus, they are reliably receiving the user notifcations as we walk around together entering these predefined regions.
My new iPhone 8 Plus, on the other hand, does _not_ reliably receive notifications, and it is perplexing. I have allowed/enabled/turned on notifications for the app, have selected the "Always" option for core location usage permissions on my device, and I have not enabled "Do Not Disturb." I have launched the Apple Maps app to verify my location is accurate, and it is accurate. I do receive other notifications from other apps (not location related) on both my iPhone and Apple Watch.
Is there a known hardware or software issue?
My iPhone 8 Plus is on AT&T, one of the 6S devices is on Verizon and the other iPhone 6S is on AT&T, and the iPhone 7 Plus is on AT&T.