now this may be to me and a friend having a server which i'm the host of, and am threw my PC not a 3rd party server hosting service. i have made the beacon a wile back about a day or 2 in real life, and left my pc on overnight for a iron farm to generate for us, anyway time isn't the problem. we have not used the /give advancement command, and are in 1.16.1, we do however have optifine enabled. i don't think that has anything to do with it but you never know. It might be with other advancement but we have not noticed. any help would be much appreciated, thank you. 

ps. the server was made in 1.16 so the transition to 1.16.1 might have broken it?