Who is to say whether it's Microsoft's problem or Samsung's problem. I suspect that their developers communicate with each other, so perhaps they can figure out who has the troublesome code. Since notifications from all other apps work just fine in Microsoft Launcher, I feel like Samsung needs to look at what is going on with their Clock app.
@TechnoStud Have you tried contacting (by phone, chat, or e-mail) either company to see if you can find anything more out about the problem? Has this always happened or did it first occur after an update (system or app)?
I recall that I imported all of my alarms from my old Samsung S9+ phone. Maybe the import messed it up versus starting fresh.
Others that are experiencing this problem... did you import your alarms from your previous phone or start fresh?
I have this issue with a 21fe, OneUI and Microsoft Launcher. Looks like I will have to get rid of MS Launcher... so annoying after having taken the time to set it up after the Google one went away...
I fixed the issue on my phone, here's what worked:
1. Use the restart option in MS Launcher (in app's settings at the very bottom)
2. In app's properties clear cache and data.
3. Don't import the old backup, it'll revert the Clock app problems.
Both methods will force you to configure everything again (apps on main screen, Launcher settings), but Clock is fixed.