[2022] Anno 1800 Season 4 part 2 not available despite purchase

Good evening dear Comunity, I have the following problem and hope for a solution in the forum.

I purchased the complete Season 4 package (Anno 1800) months ago. Now to the problem:

Realm of the Air appears grayed out in my game menu. It says the following:
Already purchased and not yet available.
Unfortunately, I no longer have my activation code!

Did any of you have the same problem and solve the problem?

with kind greetings
Jimi