@knoxploration You’ll need to create a second Calendar. Enter the time slots and the domains needed to set up a Google hangouts call.

In addition to hangouts.google.com, you probably need accounts.google.com and/or accounts.youtube.com.

Try to set up a call between a device connected to WiFi and a phone on LTE/5G mobile network connection. See what domains are blocked by Calendar in the Internet logs. Add the needed domains to the Calendar until you can establish the Hangouts call successfully.