Hey @screenager,
this has to do something with the source of the installation. OsmAnd just works with the offical official playstore version. The fdroid (full license without paying) doesnt work as i know so far:
" Android Auto is software developed by Google that allows users to connect their Android devices to compatible vehicle multimedia systems. Android Auto provides an adapted and optimized version of the OsmAnd app for safe use while driving, making it easier and more secure to access the app’s navigation functions.
** Android Auto function is only supported when using the OsmAnd app available in the Google Play store.*
** If you have purchased OsmAnd Pro from the Amazon store, you can activate it in the OsmAnd Free version app downloaded from the Google Play store.*
** After this activation, you can use the Android Auto function for which you purchased a subscription to OsmAnd Pro in another app store."*
With other apps (like Maps/Magic Earth)
Sometimes clearing Android Auto storage and then re-enabling uknown sorces worked out as mentioned here: