No mobs will spawn on my Minecraft PE ported map?

So I found this one Minecraft ported map on MCPEUniverse and downloaded it to put on my iPhone. However when I created my house and everything, nothing will spawn whether it's day or night. I tried to switch to peaceful and back, but nothing will work. Does somebody have a remedy for this? Do mobs just don't spawn on ported maps?

Somtimes it just happens or they are made to not be in it.