im on chrome book 1.20.41, i downloaded a world off of realms and /setmaxplayers wont work

im on chrome book 1.20.41, i downloaded a world off of realms and /setmaxplayers wont work, i tried downloading the world and importing it back but it just wont work, its saying it doesnt exist, the max players are 5 and im trying to change it, and nothing is working