Board Game Arena

Really want to be invited to play.. Does someone knows if I am not an alpha tester then I can only be invited through friends?

It seems that I cannot upload the image.. At the close-end time there were three empty places, I take three tiles including a brown one, but I cannot place the brown one on top of the another brown one. It is part of the rule?

I want to play the brown tile on the top of the another brown tile (bottom-right in the figure), however the system disallowed me to do so. I searched through the rulebook but not found the relevant details. Excuse me?