I retried what @BanditEagle said:
1) Press "ACTIVATE" on the server
2) Press "EDIT SERVER" or "CONTINUE" to go to your main server editor
3) Scroll down a little bit and enter the following in the console and press enter:
kill @e[type=! player]
4) Afterwards, wait a few seconds then type "save-all" in the console and enter
5) Restart the server, and try to join.
And now this is what is happening anyone please help me
631476888_Minecraft1_16.5-Multiplayer(3rd-partyServer)2021-05-1702-00-38.mp4