It must have been after a recent automatic update that Dropbox has stopped functioning well. I'm on Mojave 10.14.6 with Dropbox v168.4.4802. I have tried the various cures I've read about having to do with re-installing Dropbox, firewall settings, whitelist permissions, etc. I do have a virus app running, but Dropbox continues to misbehave even if I turn it off. I also have a very fast interconnection. What I'm seeing is that Dropbox takes like an HOUR to start up. If I leave it alone, it eventually gets going. The menu bar icon is showing that files are syncing (I think) while the icon dropdown window is still spinning on the starting up step. Worst is that until the thing clears itself, many of the files in the Dropbox folder will not open – I get a "corrupted" error message, or something of that ilk. The files do open if I jut go to the website. Plus everything is normal on my laptop where I'm running Big Sur. Please don't tell me I must upgrade my Mojave machine because there's a host of non-Dropbox reasons not to do that. I like Dropbox, but I'd be better off switching to another cloud storage app.