I know I'm writing in vain so just for the record ...
I manually flashed to version 2.5.18 and the device worked perfectly until the moment of connecting to the internet, immediately after that the black screen returned.
no syncing, no updates, no downloads - it's enough just to connect to the internet once so that the device becomes non-working.
@auc6epr Probably you are the first one who got a Google update to the newest and shiniest AndroidAuto announced for Europe a couple of days ago (already rolled out in US if my information is correct). They are driving the developers mad with their job-stopping updates every other week. No problems for me yet...
Sorry to have no better explanation, once again we have to wait until the developers will get that sorted. To force them working on that please let us know your location, your car model and year and any relevant info (e g. connecting to internet via SIM card) and start a new thread "CarPC LTE 2.5.18 (11.08.23) black screen after connecting to Internet". This will be the best tactics, if it is too much work for you judt orovide the info and I'll open a new thread.
Bye for now Fred