My Dropbox desktop app (for Mac) hasn't worked since a recent update - I've tried reinstalling Dropbox and no dice. The Dropbox website says I need the Dropbox Update app but I don't see how to install that anywhere. My web browser version of Dropbox is fine but missing recent files that I uploaded into my desktop folder - I'm also running into issues when I'm trying to open files or import them into design work. I get this error message when trying to open a file from the desktop folder:

And I do have Dropbox in my taskbar, but it's stuck in "syncing" - I've restarted Dropbox and my computer several times.
2021 Macbook Pro, Monterey OS
My Dropbox app says it's v187.4.5691
Please let me know how to resolve this - thank you!