Sensebender GW update: unknown device

[rafael156]

Hello dear Comunity!

I wanted to update my sensebender GW from 2.2 to 2.3 yesterday. after some updates windows couldn't recognize the board anymore (see screenshot). so i can't establish any communication anymore. When I installed 2.2 half a year ago, everything worked.
On the board itself, the red LED flashes from time to time. the yellow and green LEDs light up permanently.
can i assume that the cpu is defective?

My system:
Arduino IDE 1.8.5, Windows 10

Device Manager

[rafael156]

Any ideas?