Explanatory Variables fields not available in OLS tool within Model Builder

[RachelChambers1]

I'm using the Ordinary Least Squares (OLS) tool in Model Builder and one of the required fields is 'Explanatory Variables', but there are no fields to populate. I'm populating all of the other fields just like I did when using the OLS tool outside of Model Builder (and that worked). How can I make the Explanatory Variables fields available within Model Builder? Thank you!

[DanPatterson]

you haven't selected an input feature class... does selecting one change things?

[RachelChambers1]

Thanks for your reply. I deleted all fields for the screenshot, but an XY Table To Point feature class (after being projected, geometry repaired, and missing values filled in Model Builder) is the input feature class.