Dropbox authentication error with UpdraftPlus from Wordpress

[miago]

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.

[Rich]

You'll need to contact the developers of UpdraftPlus for assistance with this. Dropbox provides the API for third-party app access to Dropbox, but it's up to the developers that create those apps to support them. Dropbox cannot support third-party apps.

[miago]

The problem is an error that Dropbox returns as a result of a curl_exec call.

I am only using the basic functionality of UpdraftPlus. There is no support provided for non-paying customers.  I guess I am out of luck then and have to give up using Dropbox for this feature?

[Greg-DB]

@miago The 'BadRequestException' seems to indicate you're getting a 400 error from the Dropbox API. Are you able to print out the response body itself? It generally should contain a more useful error message. Or, please let me know if the response body is actually empty. Thanks!

[miago]

Thanks Greg for the hint!

Indeed, a 400 error is returned. I called $response = curl_exec($handle); and then printed $response.

This is what I got:

HTTP/1.1 400 Bad Request
content-length: 0
connection: close

Not sure what this means. Does it help?

Btw: I also installed on a separate part of the webserver a clearn wordpress install with the same plugin. The error persisted. This tells me the issue is either with Dropbox (something wrong with my account?) or with my host (some configuration error?).

But no idea how to proceed from here...

[Greg-DB · Accepted solution]

Thanks! That's helpful. It looks like you are getting an empty response body from the Dropbox API. We'll look into it.

[miago]

Not sure if you just fixed it or the problem solved itself. Anyway, without any further change from my side, the issue (for now) seems to be gone).

I will report back if it reoccurs. Thanks!

[Greg-DB]

Can you try again now and let me know if you're still seeing this issue? Thanks in advance! 

[Greg-DB]

It looks like our messages just crossed. Thanks for confirming it's fixed for you now.

[miago]

Yes, the issue is gone. Thanks a lot for your expert help!

Any tips about the cause just in case others in future have a similar problem (and for me to avoid it in future)?