I'm the admin of our Dropbox Business Advanced account. I already have the Dropbox app running perfectly on two Windows 10 Pro machines, and a MacBook Pro running macOS 10.14 Mojave. I haven't changed any of the account, group, or folder share permissions recently.
I recently got a new M1 MacBook Pro running Big Sur 11.2.3, and I can't get Dropbox to sync. Specifically, I can't get our team shared folders to sync. For some reason, my personal folder (that is, my personal folder within our Business account) syncs immediately, but the team shared folders appear in Finder, but are never populated. The folder icons are present, as are the right-click context menu entries. Accessibility and full disk access have been enabled. The Dropbox icon in the menu bar shows "Syncing..." indefinitely. I left it running for six hours yesterday before giving up.
Interestingly, the Dropbox desktop application shows a padlock on each shared folder and tells me that I "don't have permission to edit this folder", which is really strange.
I definitely do have access! I set these folders up, and as I write this, I can access them from my other machines without issue.
I've tried reinstalling Dropbox, both the latest stable and current beta versions. I reset all the permissions and deleted the account settings as suggested by "Dan" in ticket 12168474 which I'm cc'd on (this involved using chown and chmod to reset some permissions before doing a clean reinstall).
I've also tried everything in the accepted solution from this thread: