Maybe it's just the tilsets you're using for the parallax map? I don't really know mainly because i haven't use parallax mapping yet but i might have found a topic in the communtiy that might help with what you're looking for
(If you get confused with the script, just go to the top of the tools bar and theres an icon named script editor and you just put the script under materials)(P.S if you're STILL confused maybe search it up on youtube maybe?)
I'm still messing with it. I have been using the tilesets from that tutorial and they have been working fine until now.
My scripts are all put in right, which is why I'm genuinely confused by why I just can't walk on these tiles.
I made a new map with the parallax tileset and it still didn't work so I just gotta keep troubleshooting. It doesn't seem like many people have had this problem/it just doesn't come up in searches.
I asked in the rpg maker forums (at least, I sent a post to be approved for help) so I'm going to see where that goes.