“This app has been disabled”

I’ve re-connected loads of sites to Dropbox as per https://backwpup.com/docs/restore-dropbox-connection-backwpup-3-6-9-later/ , but now whenever I try to do it on the last few remaining sites I need to do it on I just get a Dropbox error saying “This app has been disabled” ?? (and then back in WordPress it also says “Dropbox API: (400) Bad input parameter: Error in call to API function “auth/token/evoke”: This app is currently disabled.” )

Help!