User-synchronization plugin not working. Connection problem

Hey guys,

The User Synchronization plugin is not working at all.

There were synchronization / connection problems between my master and subsite(s). Even after re-installing plugin, deleting all caches, activating debug mode, etc. it's still not working.

I've attached the error log files. For the sake of privacy I've renamed my sites into and

I've been trying to make this plugin working for more than a day, so I'm desperate and need an urgent fix or I lose the project of my client.

See attachment.