Not sure if this should be here or elsewhere - Could not upload to Dropbox

Error message
Could not upload to Dropbox: Error in call to API function "files/upload": The given OAuth 2 access token is malformed. (code: 400)

No matter what I do - I cannot get over this hump

App deployed - Folder in /apps

Key set up in Drupal Key

Destination set up in Drupal B&M

Fail every time...

Access token generated multiple times...

Allow public clients (Implicit Grant & PKCE) - turned on and off multiple times

Adjusted scoped app permissions