User Sync stopped working

Hello,
I have our plugin "User Sync" activated and connected to my Master and Sub site. I have been successfully running the plugin for a couple of weeks til it stopped working a few days ago. I have debug mode activated for the plugin and have checked my server logs for errors. I am not receiving any errors, but the sub-site is not copying users from the master.

Do you have any insight on what could be going on or how to fix the issue?

I have woocommerce installed on the master site and I am enforcing registration at check-out.

Thank you