Android Auto Connection Error 8 occurs when the Radio's Clock and Date are not matching the Android Phone's Clock and Date currently on the phone.
Radio systems with embedded navigation generally don't run into this issue, unless the GPS Time option in the time settings of the radio isn't checked, or there's a failing component in the radio that translates GPS data.
However, this issue will be possible for the IO52.5 GM HMI modules, as they do not have a GPS antenna input. The clock needs to be manually set to the Time and Date exactly as the Phone's, as close as possible to the second the minute rolls over on the phone.
Then shut the vehicle and the phone off for about a minute and then turn them both on and attempt to reconnect and should be good to go.