The solution I’ve finally come up with is that deleting ~/.dropbox/instance1/filecache.dbx seems to be the fix. I did find that deleting the ~/.dropbox folder fixed the issue for a while, but it made me reset selective sync settings and such… and when the problem came back, I didn’t want to go through that again, so I set out to find what it was in that folder that fixed the issue. Neither did numerous restarts, or repairing permissions on my Mac. button, I can then hit esc to get back out of that screen, and suddenly the Fix Permissions button shows up when I hit option. However, if I click the Selective Sync’s Change Settings. For some strange reason, it doesn’t show up on my Mac unless I first click another button on that tab. It’s hidden behind the Unlink This Dropbox button in the Account tab in Dropbox’s preferences - you have to hold down the option button to reveal it. Next, I found out that Dropbox (v2.10.30) has a hidden “fix permissions” tool. (By the way, I have to mention this great rename utility available in Homebrew, brew install rename). I found a handful of files with invalid file names, which I either renamed or deleted. Next, I tried checking for problematic files using a Dropbox-hosted tool I didn’t even know about. Unfortunately, it required me to re-set all my “Selective Sync” settings. The first few things I tried were following the official Dropbox instructions for this problem. I think it probable has something to do with me keeping a few git repositories and virtualenvs in Dropbox (mostly for the automated backup, which has come in handy).

It would show the “syncing” icon in the task bar, and if I clicked to see what was syncing, it would just cycle between tens of thousands of files to sync, then thousands, then hundreds, then just a few… and then jump back up to several thousand. I had a persistent sync issues with Dropbox for several weeks - it was running continuously and revving up the CPU on my Mac (as shown in Activity Monitor). Bottom Line: Try deleting the filecache.dbx file if you have a sync problem that isn’t fixed by following the official Dropbox instructions.

Dropbox for mac not connecting