Rosserial_python died

Hi Hubert
I flashed a new SD card with this image. After that the ttyCORE2 device was available.
Did connect an ethernet cable and than a sudo apt-get update and sudo apt-get dist-upgrade which did a lot of updates.
After that ttyCORE2 was available.
Did “systemctl disable husarion-shield” like mentioned here because I want to work without cloud. But when I try to start “roscore” I get a message something like “Could not connect to master” (I am not in front of my Core2-ROS, so the message is not exact).
What is going wrong now? The Core2 is waiting for connection (bland and yellow leds are blinking).

Michael