Character keeps falling through the ground only in a build game

my character acts fine when i test out the game in unity but once i build the game and start it he keeps falling through the ground once i change scenes

I had the same issue in 3d. What fixed it for me was removing the (mesh) collider and re-adding it. I did not change anything and have no clue why it fixed it. If you don’t use prefabs this can take some time, but it’s worth trying,I had the same issue on 3D.
What fixed it for me was removing the (mesh) collider and re-adding it. I did not change any settings and it looked the same, but it fixed it

Double check to make sure your player and ground both have 2D colliders.

Also, make sure when you switch scenes that your character spawns ABOVE the ground. If the character is even a little inside, it could fall through.