There are a lot of tasks in "starting" status in Dropbox Extension for a domain in Plesk > Domains > example.com > Dropbox Backup > Current Tasks. The tasks are in "starting" status forever and none of them ever starts.
The following errors appear in
/var/log/plesk/panel.log with debug mode enabled:
CONFIG_TEXT: ERR  Zend_Db_Statement_Exception: SQLSTATE[HY000]: General error: 1 no such table: tasks
DEBUG [extension/dropbox-backup] Dropbox Upload: /usr/local/psa/PMM/tmp/dropboxgphn3h.tar
ERR  Exception: PHP Warning: Error while sending QUERY packet. PID=667985; File: /usr/local/psa/admin/externals/Zend/Db/Statement/Pdo.php, Line: 228
Corrupted installation of Dropbox extension.
1. Re-install Dropbox: Plesk > Extensions > Check Dropbox Backup > click Remove
2. Install it back: Plesk > Extensions > Extensions Catalog > Dropbox > click Install