Thank you, PrimeNumber7 Much appreciated!
Based on the fact that you received the same message that The Pharmacist did when he tried to merit a post in a board that he didn't have permission to view (because he ignored the board), I think there may be an issue with your permissions, but I don't know what is causing it.
Thanks, I just managed to figure this out, based on your comment.
The problem was the following: I did not have German board at ignore, as I stated in OP but (big but here ) I had its sub boards on ignore. And, because of this, I could not merit that post, since it was written in German Altcoin sub-board.
And, when I checked yesterday to make sure that I do not have German board on my ignore list, I pressed "Ctrl+F" in the Ignore Boards Preferences page and typed "German". I just saw that German board is unchecked (meaning it was not ignored), without noticing that its sub-boards are ignored though...
But now, thanks to your reply, I figured it out! Thanks again! I also sent a few merits to that post made by 1miau
That's all, locking the topic now, as the problem is solved.