horizontal scroll on mobile not working

I can’t for the life of me get the responsive horizontal scroll to work. I’ve tried it on 2 different sites I manage, and I disabled every other plugin in case there was a conflict. But no matter what I do, the table won’t scroll horizontally.

SETTINGS:
Fixed columns checked
Left columns count: 2
Responsive mode: Horizontal scroll

I’ve also tried different width settings: auto table width, fixed table width 100% or 800 pixels on mobile… none of it works. With 800 pixels wide on mobile, the entire page scrolls horizontally, not just the table columns. What am I missing?