Just wanted to share my experience here. I had the same problem with my app being rejected 4 times. On my final attempt, I asked the reviewer to review once more using cellular network referencing the replies on this thread regarding potential issues Firebase (Mine uses Auth, Storage and Realtime DB) may be facing with Apple's internal Wi-Fi. Reviewer replied and asked for a screen recording of the app working and showing the features of the app (Though they did cite that I wasn't able to provide access to the app rather than being a problem on their end) I replied with the video and about half an hour later, app went into review again then shortly after it was accepted and approved. Huzzah! I suspect they are aware of the issue and are being more flexible with the matter for now. All I can say now is, don't give up, talk to the reviewer and you'll get there – Good luck everyone!