3G SDI Arduino Shield First Steps

I loaded the TallyBlink Example to try first connection to the Blackmagic Micro Studio 4k.The arduino shield I2C address is set to default 0x6E by "Arduino shield setup", the Tally Blink software is running and the Arduino shield white LED 1 and 3 are on, LED 5 (I2C Busy) does light up every second. The camera number is set to 1 (via MENU). The SDI OUT of Arduino shield is connected to SDI IN of the camera. No other connections. There is no CCU attached, no LANC or SBus connected. The Tally is set to medium intensity but doesn't blink. What can be the reason?

Problem solved. Everything works. The used BNC <-> SDI cable didn't have physical contact, which wasn't easily visible. Sorry!
Bernhard