From what i can tell this is not possible?

in my case the customer machines cannot hav any openings what so ever directly to the internet

https://helpdesk.kaseya.com/hc/en-gb/articles/229038928-How-can-I-configure-my-Kaseya-agents-to-check-in-to-the-Kaseya-server-via-a-proxy-

Workaround mentioned here is not an option in my case

its just to give up or are there any other smart  ways to solve an issue like this?