I need to write, that advice of Sergey was not correct. I got a detailed answer from firstname.lastname@example.org with folliwing steps:
1. Try to activate with the current PIN-Code. If you get a message "PIN-Code was already activated" that's okay, then step:
2. Try a new attempt with check "Computer device was not changed". (It didn't work, but it was okay)
3. New attempt without TRUE in the checkbox, using the current pin-code + reserved one.
It still didn't work, but then I guessed that company data were not complete. I added Region/County Wien (Vienna), did again the steps and everything was okay.
I just have to mention that messages of the plattform in German are a little bit irritating. In the information form is written "Owner data" but in the error-message "Benutzer-Parameter (User-Parameter) are other than entered before". I am not sure how it is in the English version of the plattform, because I usually work with a German one.
I am gratefull for the good, polite and quick help from the support of 1C Company.