Hey Google. Ok Google

[Jbug]

Google voice assistant hey Google, ok google not working with android auto since Jan beta update 

[SamsungUSABetaTeam]

Hello, Jbug.

Please try clearing the system cache and rebooting your device.

Regards,

One UI Beta Team

[TG44]

it's because your device is not official according to Google. you can check in google play