Force Sync Doesn’t Work

I have 190 WP Users, but MailPoet’s User List only shows 181. I have clicked on Force Sync numerous times but no change.

I have also noticed that even after updating a WP User’s email, the MailPoet Subscriber info shows the old email address, which I think must be related to the failure to force a sync.

I also note that the link to Force Sync shows this URL:
../wp-admin/admin.php?page=mailpoet-segments#

That doesn’t really seem like it is invoking a script or anything. Should there be more to it? How can I force a sync if Force Sync doesn’t work?