Minecraft Not Teleporting Me
Solution 1:
Registered usernames can not include spaces. As commands in Minecraft use space as a separator for arguments, they will take "Sentinel" as the name for the player to search for, and then "Gaming" as the second argument (such as x-coordinate or item) and budge everything over. This will cause an error.
If you are on a server or using some kind of plugin/mod that allows you to change your name, you should type your actual account name rather than your set nickname.
If you are using a cracked/pirated version of Minecraft, stop.
If your name contains an underscore ( _ ), make sure you are typing that rather than a space.
As an alternative to typing your name, you could use @p. For example:
/tp @p -419 43 356
This will target the closest player (which will be the person executing it), and is also shorter than typing/tabbing out your name.