Unable to allow customers to purchase additional sites for WPB. Selecting Allow customer to create trial Presence Builder websites option still does not give customers the ability to upsell, upselling button is still not available.
The following error appears:
Presence Builder is working in Trial mode because you have reached the limit of Presence Builder sites that you can publish. To publish this trial website, contact your hosting provider and upgrade your subscription
This is Plesk internal issue #PPPM-1831, which has been fixed in Plesk 12.0 microupdate #11.
Apply the latest Plesk microupdates.