This looks to me like you didn't add pronoun_backend.rpy or pronoun_setup.rpy to your project! They come from https://feniksdev.itch.io/in-depth-pronouns-for-renpy, which you need to download separately from the multi-bar code. It's got a ton of essential code to make the bar work with pronouns specifically. You will need all the files from the zipped folder in your project except for pronoun_labels.rpy, which just has examples, and you should use the included pronoun_screens.rpy from the multi-bar zip instead of the one that comes with the pronouns code if you want the pronouns screens to use the multi-bar.
Additionally, you shouldn't call the pronoun_entry screen on its own; that's just a helper screen. The screen where you can input custom pronouns is called screen enter_pronouns. I suggest you take a look at the examples in pronoun_labels.rpy; there are several examples of the screens you will need to call and the variables you will need to adjust in order to take advantage of the pronoun system.
Of course, if you're not using the multi bar in tandem with the pronouns system, you can just remove pronoun_screens.rpy and pronoun_multibar.rpy that you got from the multi-bar zip file. They're only there to integrate with the pronouns system.
Hope that helps!