watchOS 5 and Outlook 365 Calendar not syncing

Possible correction to my last post. Left work and came home and from what I assume is a network connection change, my watch now appears to be all synced up with both iCloud AND Exchange. I will keep an eye on it and report on whether that persists or if it reverts to having Exchange sync issues again.

Agreed this isn't hardware related at all. I'm seeing the same issue on series 3 and series 4. Not sure how hardware would differentiate exchange vs iCloud calendars anyway.

For people who seem to have this issue one day and not the next, for me it seems to be when past calendar events TTL that happen to be the corrupt events that other users described.

Yep, I've had this problem with my watch too: Series 4 44mm non-cellular, watchOS 5.0.1, iPhone XS, iOS 12.0.1

Random events from my work exchange calendar show up but not all of them (this is pure on-prem Exchange/ActiveSync not Office 365). I've tried turning off some of my other calendars, rebooting the watch and phone, resetting the sync data, unpaired and repaired the watch as new. Nada. Also, my iCloud reminders seem to randomly show up sometimes but mostly aren't there at all. I am assuming that is related as well. Really shoddy given the number of folks I've seen complaining about this as I've searched for a solution.

Right before the weekend, mine spontaneously started working. All calendars present, all reminders there. Nothing winking in and out. I was quite happy and assumed it was a back-end thing that had been fixed.

And then I noticed I couldn't swipe down on the watch face for notifications, or up for control center, or left-to-right to change watch faces... Complications still launched, and the digital crown and side button worked but the rest didn't. I actually considered leaving it that way for about an hour before I finally gave in and restarted the watch. Everything else started working but the Calendar and Reminders were hosed again. Then I also noticed when I created some reminders via Siri on the watch, they didn't make it back to my phone or iCloud which is a big problem for me and the first time I've seen it (though I suspect it may have bit me a couple of times where I thought I'd created a reminder for something).

As of today, the Calendars all seem to be there, but it still says I have 0 reminders on any list even though I have about a dozen active ones right now. (Also, all reminders are iCloud-based, none are Exchange/Google synced items.)

I have been in contact with apple support -case # 20000031151013- and I have updated both my watch (series 4) and my phone to the news iOS. This has not helped the syncing problem with the watch and outlook 365. Very frustrating. I have tried all the suggestions but not updating the events. I installed 24me and can see the events in the app on my watch.hopefully they find a fix soon. I like having the calendar on my watch.

well - i updated my Apple Watch 3 this morning to 5.1, before that I updated my iPhone 8+ to 12.1.

First go looked promising with the built-in calendar app, all my appointments of the upcoming day were there. Adding new appointments on the phone went fine, instantaneously they appeared in the calendar complication on the watch as well. But deleting an appointment on the iPhone did not make the corresponding entry on the watch disappear. Could be reproduced with more appointments and both with the O365 calendar and the Apple calendar.

Thus I decided to de- and recouple the watch again, to have a fresh start.

After that I'm back to the annoying behaviour of last weeks - only tiny part of my appointments (randomly chosen, it looks) are propagated from the iPhone to the watch. Adding, changing, and deleting appointments on the iPhone has no effect to what is displayed on the watch.

Absolutely disappointing, dear Apple guys!!! I'm really losing trust in that what you are doing here. The major use case of the Apple watch was and is to have a reliable "wrist"-extension of my "office" that i have on my notebook and my iPhone, and that means a working calendar app is the thing I bought my first Apple Watch for 3 years ago, and 3 months ago my second to replace it. And I was absolutely content with both watches until the switch to WatchOS5 messed all up. And I'm pretty sure I'm not the only one feeling like this about this issue.

Now about 24me - fine application, I like it very much - only with one flaw at least on my Apple Watch 3 - the complication only updates what they show when i switch to another watch face or when I open the 24me app via finger-tipping its complication. If I don't do that, the appointment shown in the complication stays all day the same, even if there would be newer ones to be shown.

Really frustrating all this.

So that's interesting - see my post above. I don't have any Profiles on the device (unmanaged non-enterprise configuration) and I was told it's a known issue that is being actively worked now that they've identified it

Yep I did...also found this thread with similar issues:

Watch OS 5 Calendar | MacRumors Forums

Exchange Admins will definitely reject it since 24Me, a 3rd app, works fine, load calendar events and show them in the watch os face.

I've found the same. Checking and unchecking calendars has no effect as once the Exchange account is added, changes made on the phone (whatever they might be) don't get synchronized.

I have the same problem using my iCloud Apple calendar AND Outlook Exchange. Completely unreliable. Same watch series2, WatchOS 5 and IOS 12. Tried everything you did to attempt to fix. No luck. I DO get notifications for calendar appointments I can't see on the watch, but do appear on my iPhone 6s. I have tried mirror and custom for the calendar events, neither works.

It just does not work.

That may be turn out to be the case for MS problems, as I believe 11.4.1 included a patch for Exchange. However, my iCloud calendar works no better than Office 365. I think there is an underlying problem which goes back years as some appointments sync, but not consistently. It "may" have been fixed in the past, but it's broken again. I will be contacting apple support tomorrow.