Has anyone had this problem?

Basically, when people connect to the server, all their pokemon and such are there, the world is there, but you are unable to move. When F5 is pushed you also just show invisible. It’s literally like you arent there.
What should I do

if region just things taking long to load in .Adjust the server map, or modify the client can be fixed?

Im not a forge guy myself, but if it is due to everything loading in, you maybe able to reduce the amount that is required to load in by lowering the server render distance. This will reduce the amount of chunks being loaded around a player. You can reduce this in the server.properties file