I can't go in 1.20 chunks

Here I am playing Mincraft but then I see 1.20 chunks I go in them but the server crashes but the client does not so i can move but not place or break blocks, load more chunks or anything but some 1.20 chunks work but when i go like 10 chunks in the server fails! Also this is a old world so i could be just me and a few years ago i enabled "EXPERIMANTAL GAMEPLAY" I did not know i would keep the world