BACKUP S3 stop working (v0.26c)

After the version update, the backup interface appeared: “Something went wrong, sorry.”

And I find the backup disabled.

Then I tried to reconfigure the S3 backup, but the message appears:

“<! DOCTYPE HTML PUBLIC “- // W3C // DTD HTML 3.2 Final // EN”> 500 Internal Server Error </ title>

Internal Server Error </ h1>

The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application. </ P>”

What can I do to restore the backup?

Does anyone have any solutions about it?
Is Amazon S3 still supported by mail-in-a-box?
Thank you

Can you please send me the /var/log/syslog file in a PM only please?