Every time I type anything with "/LP" in it, "[LP] running luckperms v4.0.18" shows up. This happened last night as well. I tried deleting the plugin and the folder to regenerate everything, but that didn't work. I ended up having to download the same version again and it fixed it.

12hours later, the same issue is present. There's no errors in the console.
I'm using latest LP version with spigot 1.12.2

First line of https://github.com/lucko/LuckPerms/wiki/Command-Usage states:

If the only thing returned when you type a command is the plugin version, you do not have permission to use any of the commands. You need to use the server console to give yourself access to LuckPerms commands first.

If there aren't any other messages being sent in console, then that's what the issue is.

This includes all commands starting with "/lp"

giving myself OP doesn't work?

Which platform are you using? Bukkit/Spigot or Sponge?

Spigot. I op'd myself again and it works again. Thank you