Unable to retrieve the backup from Dropbox: The server has either erred or is incapable of performing the requested operation

Symptoms

Listing or downloading backups from Dropbox intermittently results in one of the following error:

PLESK_ERROR: Could not display the list of backups in the Dropbox Backup storage: Unable to get dumps list: Transport error: Extension transport: ext://dropbox-backup/server:

PLESK_WARN: Could not display the list of backups in the Dropbox Backup storage: Unable to get dumps list: Transport error: Extension transport: ext://dropbox-backup/server: {"error": "The server has either erred or is incapable of performing the requested operation."} . Please check the storage settings.

Cause

Dropbox returns HTTP error 500 periodically. The impact of that on Plesk backup manager is registered as Dropbox Backup extension bug #EXTPLESK-1582. It is planned to be fixed in future product updates.

Resolution

Until the fix became available, use the custom extension build.

1. Download the custom extension build;
2. Log into Plesk;
3. Navigate to  Extensions > My Extension click Upload Extension and select the downloaded extension.