Thanks for your support!
I found out what was the problem:
During the activation, I usually set the TB date ("Date activated") to a special date in the past, e. g. to the date of my birthday when I received the coin.
That's what I also did for the current "81 Grid Champion" coin.
But obviously, if this TB date is not in the "timeframe" of the current FRIEND LEAGUE action this leads to the issue that no points will appear. So, I fear that geocaching.com does not use the actual activation date but the TB date what is being entered by the user during the activation process.
Solution:
Activate the TB with activation date <today>. I did this for the next TB and received the points. :)
The date can be changed later by editing the TB.
