Help me with a mod nickname

Hello, good evening, I wanted to ask about a mod for a label I'm working on. well this goes like this, I want that when I point to a mod/entity, using an item (nicknameMod) when I click on it, it opens the menu of the gui that I have already created, once I put the name, below there is a button that It says (ready) when I click on it, I get out of the gui and the entity is named, I did everything but it won't let me name my pet, what can I do? Please I need help since I have been dealing with this for several days and no one responds to me on any social network. thank you