I've checked the AddonOn against both the current live client, and the Beta client, and I can't spot any issues. Seems to be working just fine in both of them.
If you're experiencing problems, please try clearing out the AddOn data and see if that solves it. It's located in a file called "XToLevel.lua" inside the "WTF\Account\<ACCOUNT_NAME>\SavedVariables" directory of your game installation. Deleting/moving that file will cause the AddOn to re-create a fresh one next time you log in.
If that doesn't help, please open a ticket on CurseForge and give me some details about your situation. If you get any error messages, those are extremely useful.