Just to double check, after unzipping there's a StreamingAssets folder inside the Incarnasoul_Data subfolder?
If so, so long as you're on Windows or Linux it should work. Is the message about downloading the assets showing on startup?
That sounds right.
I'm not too sure what could be going on as a one off - could you possibly have the patch zip instead of the full zip?
It might also be worth trying a redownload of the assets anyway in case something went wrong with the file randomly - the direct link is https://mega.nz/file/LnZWyDoD#gSMjN9SB_Qd16H05pngh8rCQE0Sm-xR6bJW9xEKMRBA