I have been using the Remote Storage option from within the UpdraftPlus plugin in Wordpress to keep backups on my dropbox account for several years. After moving my website to a new provider, the upload to dropbox stopped working. I checked that the connection to Dropbox is set up correctly by removing the settings for Dropbox and reauthentication. I can access and download from Dropbox old backups in the plugin without problems. But any attempt to upload files fails.
The following error is returned:
0020.397 (0) Dropbox: Attempt to upload: backup_2020-05-14-1059_MyWebsite_5b250aabb84c-plugins.zip to: backup_2020-05-14-1059_MyWebsite_5b250aabb84c-plugins.zip
0021.240 (0) Dropbox chunked upload: 6.2 % uploaded (AAAAAAAAE7XIXgypxcVeOA, 1048576, 9216 KB)
0023.780 (0) Dropbox chunked upload: 61.6 % uploaded (AAAAAAAAE7XIXgypxcVeOA, 10485760, 10240 KB)
0025.721 (0) Dropbox chunked upload: 100 % uploaded (AAAAAAAAE7XIXgypxcVeOA, 17034343, 10240 KB)
0025.766 (0) Dropbox: chunked upload exception (Dropbox_BadRequestException): (line: 225, file: /home/MyWebsite/wp-content/plugins/updraftplus/includes/Dropbox2/OAuth/Consumer/Curl.php)
0025.767 (0) An error condition has occurred for the first time during this job
It appears upload is started correctly and runs up to 100% but then does not complete or fails with some form of authentication. This problem occurs repeatedly and identically for every upload.