nether portal dont work

Im running fabric (world is set to fabric, cant change) and only one mod which i checked, it does not affect the nether. I stand in the portal and it does not teleport me. I read a post where a staff member said to replace the file level.dat with something else (Roman) and i did that but when i uploaded the world it reset back to what it was. If Roman is reading this, you'll probably know what im talking about.