Yeah, that 'Loading profile...' screen that sits there for ten minutes (or forever) is maddening. I've seen it on more client machines than I can count, especially after a Windows 10 feature update or a cumulative patch. Good news: it's usually not your mailbox or server. It's a corrupted cache or a profile that's stuck. Let's fix it.
The quick fix that works most of the time
First, close Outlook completely. Then open File Explorer and paste this into the address bar:
%localappdata%\Microsoft\OutlookLook for a folder called RoamCache. Delete it. Don't worry, it's just temporary data that Outlook rebuilds. Then restart Outlook. Nine times out of ten, it'll sail past the loading screen like nothing happened.
If that didn't do it, try the nuclear option — rebuild the profile. Go to Control Panel > Mail > Show Profiles, select your profile, and click Remove. Then create a new profile and add your email account. You'll lose your cached email, but your server-side items are safe. Clients freak out about losing contacts, but they're synced to the server (Exchange, Office 365, IMAP). I've done this on a client's machine while they watched, and they were back up in five minutes.
Why this works
When Windows Update runs, it sometimes invalidates the pointer to Outlook's profile data. The 'Loading profile...' hang is Outlook trying to read a corrupted cache index. Deleting RoamCache forces Outlook to rebuild its local cache from scratch. Rebuilding the profile clears any corruption in the registry and forces a clean start. It's a clunky workaround, but it's the standard fix until Microsoft patches these update interactions.
Less common variations
Sometimes the fix is simpler: a stuck COM add-in. Hold down Ctrl when launching Outlook, then choose 'Yes' to start in Safe Mode. If it opens fine, disable add-ins from File > Options > Add-Ins. This is rare after an update, but it happens.
Another one — a corrupt OST file. If you're on an Exchange account, close Outlook, navigate to the same folder, and delete the .ost file. It'll rebuild. Just know it'll take a while if your mailbox is huge. I had a client with a 50GB mailbox and that rebuild took two hours. But at least it worked.
Also check if there's a lingering Outlook process in Task Manager. Sometimes Outlook doesn't fully close after a crash, and the next launch just waits for the zombie. Open Task Manager, end any Outlook process, then try again.
Prevention for the next update
Before the next Windows Update, do a manual check: run Windows Update, but pause it. Then close Outlook and run the update. Sometimes the update messes with Outlook's files while it's running. Not always, but it's a cheap precaution.
Also, keep Outlook updated. Go to File > Office Account > Update Options > Update Now. Microsoft has patched several of these update-related hangs. A client of mine ignored updates for six months, then a Windows Update hit and Outlook wouldn't start. The fix was updating Office to the latest version.
Finally, if you're in a corporate environment, make sure your IT team has the latest Windows 10/11 quality updates. Some of the earlier cumulative updates (like KB5005565) caused this exact issue. Later patches fixed it. So keep both Windows and Office current.
That's it. Next time you see 'Loading profile...', don't wait it out — hit it with the cache delete first. If that fails, rebuild the profile. You'll be back to email before your coffee gets cold.