If you are trying to check your ping... you can type /ping Then when the chat replies "Pong", that is your ms. The time it takes to reply indicates your ping. every second is 1000ms. So if there is a half second delay it is 500ms Instant means your ping is fine. If there is a delay, that means you ping is high. You can also see your ping to the server on your multiplayer tab but this is not accurate because it does not take into account the blocks around you in the world.
I always just type / and wait to see how long it takes to say the command is unknown much easier then ping pong. I guess there’s probably some reason that’s bad for the server or doesn’t work as well though isn’t there