Resolution
Linux:
It can be done with the following command line:
[<MYSQL_BIN_D>]/mysql -uadmin -p`cat /etc/psa/.psa.shadow` -D psa -e"update misc set val='false' where param='disable_updater';"
Please see the KB #952 regarding the placeholder <MYSQL_BIN_D>.
Windows:
Follow this article to access 'psa' database:
3472 [How To] How to access Parallels Plesk Panel database
Once inside, run this query:
update misc set val='false' where param='disable_updater';