I have a custom tab for a custom object that is used regularly in our org. We are making the switch to Lightning, but I cannot get this one tab to show up in Lightning. It is available in classic and I can access it from the waffle icon in Lightning. Below are some screen caps of me adding it to our Lightning navigation menu. I've set everything else up the same way and it is working fine. Any thoughts on what I could be missing?

I have a custom tab for a custom object that is used regularly in our org. We are making the switch to Lightning, but I cannot get this one tab to show up in Lightning. It is available in classic and I can access it from the waffle icon in Lightning. Below are some screen caps of me adding it to our Lightning navigation menu. I've set everything else up the same way and it is working fine. Any thoughts on what I could be missing?