Those who tried to take part often got an error message that said the program was maxed out.
Google is expanding the program, giving anyone with an Android device and a willingness to put up with bugs the opportunity to test the platform's latest features before they're available to the public.
"As a beta tester, you can help us build a better version of Android Auto.
You can join the program by visiting the beta opt-in page Google has set up.
Click the "Become a tester" button, and then download the beta version of Android Auto from the Play Store.
If you eventually decide using unstable software isn't all it's made out to be, you can leave the program.
With Google inching closer to the official release of Android 12, the company likely wants to avoid a repeat of last year's Android 11 release.
While the operating system was buggy as a whole at release, Android Auto suffered from some particularly rough bugs.
So it's no surprise Google wants more help testing the software.