Do the models contain sub models? Each brick needs to be in the main model. Therefore, you need to open it in Stud.io (or another software), select a sub model and click on release in the lower right corner of the viewport. Do this with all sub models and it should work.
Their models have not been imported into the game. If you post the missing IDs here (https://itch.io/t/238206/missing-bricks), I will add them as soon as I can. The IDs are automatically saved in a text file in the game's directory, so you can simply copy the content in the thread linked above.