HELP - connected but can't access internet on wifi hotspot

I have an appradio 2 and a nexus 6 so i must use a chromecast to mirror my phone's display to my radio since the nexus 6 does not have mhl/slimport

thus, i have to turn my nexus 6 into a hotspot, connect a 2nd phone to the hotspot, and then setup my chromecast. i can setup the chromecast no problem - but after setup i always get the error message "connected, but can't access the internet"

now, the hotspot is still active and working i can connect other devices and they work no problem.

any idea of what the problem could be? this is driving me nuts and it makes my radio worthless if i can't get it fixed

thanks