Hi Lain,
Thank you for your help. ;-) Now I've finally managed to connect. My mistake was to turn on the live view before connecting. It no longer works in conjunction with AA+!
It also takes a while for AA+ to check everything, so patience is necessary.
One more thing: I don't understand why AA+ has a special DSLR 2.2 jack input, but it doesn't work and the image transmission output has to be used instead. This is confusing.
Finally it works and I hope it helps other Nikon users. Best regards from the cold Germany, Helmet