How can I make my mob spawners work?

Question

In Minecraft Bedrock, I built 2 mob spawners. One the drops 20-something blocks underground (I don't remember how many, but I followed a tutorial) and another above ground. The above ground one is bright inside even though there are no holes. I made both of cobblestone. I had the same issue with the first one I built a while back. The underground one is completely dark inside, I went and lit up all nearby caves and still no spawns. I have gone to the other side of the map as well so I know I'm not too close.

Answer 1

The reason is because mobs only spawn from 148 blocks away from caves, if it is closer, the mobs will spawn in the caves instead of the mob farm. There's a solution to this. You can build the farmer on the ground but only if you lit up all the caves and dark spots in a 148 blocks radius. You can do one out of the two, either build it high up or build it on the ground and lit the caves in a 148 blocks radius, it's up to you. Wish you good luck!