Why Do Random Objects Become Invisible And uncollidable? (Answered)

i was trying to make a game but when i clicked the play button to test it the floor was not there. at first i though the spawn was glitched but it was not that. i clicked on play here while i was above the platform and i fell through the platform and it was also invisible. this only affects random things because i was also adding a tree into my game and everything except the tree was visible but the tree was invisible and i fell through it