backup failed

You receive an email notification about a failed backup.

You check Acronis True Image user interface and all indicates that all backups have completed successfully :

green check box is displayed on each backup
backup completion confirmation is displayed under Activity tab for each backup
a new recovery point under Recovery tab is added as date and time of a successful backup (right upper corner)

Symptoms

Backup or another activity fails with the following error:

Operation failed due to a temporary issue in the cloud storage.

In Error Details of the error, the following message is being observed:

In on-premise Acronis Cyber Protect 15, backup and other activities to Cloud fail with the following error message:

"The request failed: Status 503: Description: Service unavaliable"

Issue in the product.

The issue has been solved.