Back-up error and doesn't do the back-up

I am using Nextcloud on Yunohost and I have set up back-up on one other Nextcloud (which is on bare metal). But back-up just doesn’t work.
Log file says this:

{"reqId":"M906syFxwVDX76svrWFC","level":3,"time":"2022-10-14T23:45:13+00:00","remoteAddr":"","user":"--","app":"backup","method":"","url":"--","message":"error while running differential backup - [{\"file\":\"\\/var\\/www\\/nextcloud\\/apps\\/backup\\/lib\\/Cron\\/Backup.php\",\"line\":126,\"function\":\"runDifferentialBackup\",\"class\":\"OCA\\\\Backup\\\\Cron\\\\Backup\",\"object\":{},\"type\":\"->\",\"args\":[]},{\"file\":\"\\/var\\/www\\/nextcloud\\/apps\\/backup\\/lib\\/Cron\\/Backup.php\",\"line\":115,\"function\":\"runBackup\",\"class\":\"OCA\\\\Backup\\\\Cron\\\\Backup\",\"object\":{},\"type\":\"->\",\"args\":[1665791113]},{\"file\":\"\\/var\\/www\\/nextcloud\\/apps\\/backup\\/lib\\/Cron\\/Backup.php\",\"line\":97,\"function\":\"manage\",\"class\":\"OCA\\\\Backup\\\\Cron\\\\Backup\",\"object\":{},\"type\":\"->\",\"args\":[]},{\"file\":\"\\/var\\/www\\/nextcloud\\/lib\\/private\\/BackgroundJob\\/Job.php\",\"line\":54,\"function\":\"run\",\"class\":\"OCA\\\\Backup\\\\Cron\\\\Backup\",\"object\":{},\"type\":\"->\",\"args\":[null]},{\"file\":\"\\/var\\/www\\/nextcloud\\/lib\\/private\\/BackgroundJob\\/TimedJob.php\",\"line\":60,\"function\":\"execute\",\"class\":\"OC\\\\BackgroundJob\\\\Job\",\"object\":{},\"type\":\"->\",\"args\":[{},{}]},{\"file\":\"\\/var\\/www\\/nextcloud\\/cron.php\",\"line\":151,\"function\":\"execute\",\"class\":\"OC\\\\BackgroundJob\\\\TimedJob\",\"object\":{},\"type\":\"->\",\"args\":[{},{}]}]","userAgent":"--","version":"24.0.5.1","data":{"app":"backup"},"id":"634c46e7855f6"}

Maybe I didn’t configure it right, but I followed the instructions.
Thanks

No one has any idea?