macOS apps unable to load Open… and Save as… dialogs [seemingly due to Dropbox]

On Monday, I noticed that my web browser had 4 incomplete downloads after hours (which were just PDFs I’d tried to download), and I couldn’t figure out why. Similarly, when I’d right-click on an image to ‘Save Image as…’ a dialog would never show. However, I could drag images from the browser to the desktop. After a couple of hours, I restarted the Mac, but it didn’t fix things. I then opened a picture in an image editor to touch up an image and save it… but when I clicked Export (which triggers a Save as… dialog box)I got the beachball spinner but no Save dialog ever appeared. After about 1 minute, the beachball disappeared and the app was usable again, but the file was never saved. Then I went to TextEdit to open a file, and I couldn’t get the Open dialog to open. Then I went to Safari to download a PDF, clicked the download icon on the PDF, and no dialog appears. All these apps freeze up with the spinning beach ball when I go to Save as…/Open…, and after ~1 minute give up and return me to the prior state, never open the Open or Save dialogs, and never message me as to what’s going on. 

To be clear: dragging a document onto an app DOES open the file, and I was able to Save (just not Save as… where a destination-target dialog would open). 

Note: I have a MacBook Air M2, running latest Sonoma 14.4.1, so no ability to zap NVRAM or SMC 

I found several things on Apple support forums but none worked…

1. Reboot Mac — issue persists
2. Unplug Mac from all peripherals and power, reboot — issue persists
3. Run ‘killall Finder’ and ‘killall Dock’ — issue persists
4. Uninstall the 2 apps I’d installed shortly before noticing the issue — issue persists
5. Pruned non-critical and unrecognizable elements from ~/Library/LaunchAgents, /Library/LaunchAgents, /Library/LaunchDaemons, and /Library/StartupItems — issue persists
6. Change primary display to MacBook (not external monitor via dock), reboot — issue persists
7. Sign out of iCloud, reboot — issue persists
8. Shut down, startup in Safe Boot from the Recovery utility — issue persists
9. Reinstall macOS Sonoma from the Recovery utility  — issue persists

I then created a new device User (System Settings > Users & Groups > Add User…), and switched to that new User. The issue does NOT reproduce in the new User profile, but remained in the original User profile when I returned to it. So clearly something is wrong in just my primary User profile. Apple Support suggested I create a new User, and move all data over and reinstall all apps. Before taking on that ordeal (having already lost 1/4 of the day to OS reinstall), I tried one more thing…

I reviewed Console and discovered several “Failed to find resources for…” messages for Dropbox and Google Drive. I quit Dropbox from the menu extension, removed Dropbox entirely (from /Applications, ~/Library/ and ~/Library/Application Support/ . Then I quit each currently-open app on macOS as I saw some newly-opened apps work but already-opened apps still had the issue. Once all apps were closed and reopened, every app was able to ‘Open…’ and ‘Save As…’ again just fine. 

What was special about Dropbox? I’m not sure. I had just finished moving all my files from Dropbox to Google Drive early in the day when the Open…/Save as…issue appeared, which is about the only notable change to Dropbox state that I’m aware of. So, in any case, for anyone else discovering an issue like this in the future: consider fully quitting and removing your Cloud storage app temporarily (as your files should be synced there already and can be re-retrieved afterwards) as a far simpler troubleshooting step than most of the steps I tried above.