So my site needed dropdown menus for selecting "Size" and "Color" attributes. Nothing worked until I went to the "Variations" tab that's in the individual product edit page. I clicked on "Bulk Edit" drop-down then "Prices" and then entered a value in the pop-up. Works like a charm now.
Don't think you even need to select "Bulk Edit" and "Prices", you just need to set a value in the "Regular Price" field and that should fix the errors, at least it did for me.