Please add way more details, otherwise nobody can help you.
- what devices
- do you use an app
- do you use android auto
- did you need to do anything special before
- exact error messages
Best would also be system logs. You can use LogFox from F-Droid for that. Use F-Droid Basic as client, the one advertised is outdated.
Enable logfox over adb, you will have adb somehow or a working device where you can install adb.