Do you by chance have another skin to test with? In case it's just that one.

I wasn't sure if skins were meant to work this way, but I found a news post that they are.

Just saw your edit!

Can you check if the older zombie skins give access to the Zombie Den? Example: dolly dreadful & doom bloom

Can you test to see if you can get in with one of those skins? indicated they were able to!

Awesome!

Thanks for testing this!

Locking as resolved. :)