muellerlamicka The issue with the missing content messages has been going on for a little while. It seems to be a non-issue from what I can gather as in almost all cases, everything is there if the packs are owned and enabled. You've said that the content is missing in the lots when you place them. So, the question is: is it the gallery download(s) or is the game itself not seeing the packs. Here is the bug report on the messages:
[GALLERY] 'Content not installed' warning with all content owned | EA Forums - 12640662.
And another on the game not seeing all packs owned:
Packs/Worlds showing as deactivated in-game/Not active after purchase | EA Forums - 13261188
Please take the time to read and upvote the one that most closely describes what is happening in your game.
There are a number of other posts, not in the bugs forum, that cover the same or similar things so you could also search the forums if you care to.
As to how to fix the issue, you can try some of the things in those posts. Before you download next, make sure that all your owned packs are active and see if the downloaded lots continue to give you messages or are missing content. I tested by downloading a few lots from the Gallery, but I did not have any problems (no messages, all content was there) so Idk what else to suggest. Sorry.
Hope this helps.