Arduino Uno. R2 RX TX LEDs and not loading sketch

Hello,

the RX Led on the Uno shuld start flashing once talking to the Uno as seriel Interface?
I use Hterm on windows with baudrate 19200, 8 Databit, 1 Stopbit, parity 0.
The Uno is properly detected as serial port but nothing loops and no rx/tx led flashes.

My Problem: I always receive the error when tryig to load a sketch
avrdude: stk500_getsync(): not in sync: resp=0x00
Settings in Ardiono IDE (Board and Serial interface) are correct

Bootloader has been upladed to the Mega328 by ISP and Fuses of the Mega328 have been verified.

I am starting to think the second onboard atmega16 (usb-serial brige ?) is not working properly which leads me back to my initial question: If the RX led is not blinking on a loopback test or when trying to load a sketch, there is something wrong?

Regards
Christoph

Is the 328 getting reset as part of this? Either from software via the DTR, or manually via pressing the reset button.

I am not sure, this should happen automatically on the uno?

I tried resetting it manually right after build was complete, no change. I will try to verify the reset with a scope today.