Outlook on iPhone stuck on downloading messages from Microsoft Exchange

Question

On the evening of Feb 12, I stopped being able to send emails from Outlook (v4.2404.0) on my iphone 15 (iOS is up-to-date). They just sat in my outbox. New messages were not being downloaded, although my badge notification was reflecting the accurate number of unread emails I had, even though those emails were not visible in my inbox. Outlook on my desktop and Outlook webmail are fully functional and have had no interruptions in functionality. I uninstalled Outlook on my phone and reinstalled it. Adding my account back to Outlook triggered the Microsoft Authenticator and then the account was added and I got the screen that says "Downloading your Messages." There is no evident progress in the download. The email server is Microsoft Exchange. I have about 31k emails in my inbox (totalling about 25gb), but I let the "download screen" stay undisturbed overnight and there was no evident progress. I get no error message; simply this claim of downloading with no progress. There is a gray bar at the bottom of the screen that says "Updating..." but it also gives no real indication that anything is actively happening. I've tried resetting the account in Outlook; I've tried removing and re-adding the account in Outlook; I've tried disabling the two-factor authentication and re-trying all these steps; I've uninstalled and reinstalled Outlook multiple times; I've rebooted my phone multiple times. My subscription is Microsoft Business Professional through Godaddy. Godaddy has tried to help some (seems I cannot get phone support directly from Microsoft due to the nature of my subscription?), and I have an open ticket with them, but the first guy I talked to sounded like he was basically just Googling all the things I had already tried. I removed my phone from the list of mobile devices in my online admin portal, and none of these efforts to get my phone Outlook to re-sync with my email have resulted in my phone re-appearing on that list. I've also tried manually adding my account back to Outlook (i.e. without using the authenticator and just punching in my username/password and domain information). I have made no recent changes to my account. My employee, who also uses Outlook on his iphone, has had no issues.