Jonathan Herring

The command input field represents the command to be run, @a is a selector which refers to all players in the world so that command should work fine. The previous output field refers to what happened the last time that block was run, so if you're on singleplayer that should probably be the last map developer to test that command block before uploading the map.
The reason it didn't work is that command selector arguement "@a" has a specifier in it's list to only teleport players in adventure mode "m=a" aka mode=adventure, since you are in creative mode the command did not teleport you.

Essentially you need to be in adventure mode for the map to work properly.

Beacon's do not give off their column of light even in regular non-rtx enabled worlds in this version