blbbuyer wrote:
I transferred all data from my backup to my new Mac. Dropbox appears in the list of Applications and in Finder though not in the menu bar. I can see the folders but can't open them to access the files. The message says "can't find account".
hmmm.. never had an issue with Dropbox. Did you quit the Application and relaunch it. The menubar access is an option and a relaunch should reset it to launch at start up login
In Finder— if you Control click it gives you options...

for your third party app—if in doubt search the developers website or contact their: Support/Help/FAQ/Known issues/compatibility/updates…
Contact a third-party vendor - Apple Support
Contact a third-party vendor - Apple Support
https://www.dropbox.com/support