Hey @Naomi_Adkins, thanks for reaching out!
We've had a similar report about scrubbing not working on a color stop's opacity value in a gradient, and that one's since been fixed. So if you're working with a gradient, it's worth checking you're on the latest version of Figma to see if that resolves it.
If it's the percentage value itself that won't scrub at all, that's actually expected, that particular field was intentionally set to type-only a while back, after it was found to interfere with neighboring fields when dragged.
Could you confirm whether you're working with a plain color fill or a gradient, and whether you're on the desktop app or in browser? That'll help me point you to the right next step.
You can find more on working with fills in Use gradients as a fill or stroke.
Let me know how it goes!