Your iPhone and mac must be on the same wi-fi network (2nd take)
I am making reference to a previous thread with many entries as today I came across the same issue.
Trying to make (or receive) calls from my Mac does no longer work and I am getting the deceptive message “iPhone and Mac must be on same network“.
I tried all the tricks up to my sleeve (disconnecting and forgetting network, resetting and restarting all devices and network) nothing did work until I reverted back to my old network based on an Apple AirPort Extreme and connected my devices to the 5 Mhz network.
Please note that I was in the process of upgrading to a brand new LTE based modem/router.
So, in my particular case it appears to be a router issue.
Please note I have to fairly dated MacBooks a 2012 Pro (works like a charm) and a 2017 Pro running respectively Catalina and Ventura.
Hope this helps
/P
iPhone SE