I just upgrade Joomla from 4.0.6 to 4.1 and before to proceed, Akeeba backup failed to upload to OVH.
I changed the credential at OVH to test and same problem.
It could be a problem from OVH, but right after this kind of major upgrade (J4.1) I doubt it is.
Anyway, here is the message I got from the logs. May be it could help you, if the problem is on your side.
INFO |20220215 12:08:44|Beginning post processing file <root>akeeba-backups/site-home.humanity.net-20220215-070822est-g1HYqyFAJzA9wDBp.jpa
DEBUG |20220215 12:08:44|Authenticating to OVH
DEBUG |20220215 12:08:45|Uploading site-home.humanity.net-20220215-070822est-g1HYqyFAJzA9wDBp.jpa
WARNING |20220215 12:08:45|Failed to process file <root>akeeba-backups/site-home.humanity.net-20220215-070822est-g1HYqyFAJzA9wDBp.jpa
WARNING |20220215 12:08:45|Error received from the post-processing engine:
WARNING |20220215 12:08:45|<html><h1>Unauthorized</h1><p>This server could not verify that you are authorized to access the document you requested.</p></html>