ACC Multiplayer Cars not driving

[Skyraker]

(Sorry, german)
Hi,
my ACC Multiplayer wont work and i hope you can help me.

- I start the game
- I go to Multiplayer
- Servers listed with a fine Ping
- green light on the right bottom is on and says connected
- I join a server and i got in without problems.

But now, all cars are staying at their boxes. The server stats are showing zero.
I am able to switch between the drivers, the times and driverpositions are running and updating, but the cars wont move. I can drive, but there is no one on the racetrack.
After some time the massage that i was disconnected from the server pops up.

What have i done?
- Repaired ACC in steam
- Reinstalled ACC several times incl. deleting all subfiles and without a Firewall
- Updating Windows
- ACC Ports at the Router are free
- No new Firmware for the router available
- Internet is ok (400mbit) and running stable

New Software? No, two days ago everything worked fine. Yesterday i checked out some rounds in AMS2 (installed a long time ago and also played time by time).
Then i started ACC, copied some "go setups" into documents...acc...setups, and drove some singleplayer rounds. After that i want to start a Multiplayer, but it dont work.

CPU 11400F and a RTX 3080ti are ok and never made failures.

Any Ideas?
Thanks a lot
Tom