Is it plastic or weed barrier cloth? Plastic will work, if it doesn't have holes in it -- but-- if it has been down a long time and sand and dirt has accumulated on top of it, weeds can and will germinate and grow in that stuff on top.
Weed barrier cloth is a different story. Weeds will not only germinate on top of it, but will put their roots right through it. It really isn't much of a barrier.

As for the preventive, I think it depends on what you are using, but the general idea is whether the chemical (or corn gluten) is in contact with the seeds, not if it is in the soil so much.

Thx for follow up.. It is definitely plastic as I've planted a couple trees in the area and cut out areas.

I use Amaze granuals. The price of it has increased quite a bit but Its worth it for sure. I didnt put it down this season and am paying the price now. Like mentioned above if there is enough soil on top of the plastic for seeds to germinate then the granules will help you out.

The plastic traps dust and organic debris. You end up with a thin layer of soil above the plastic and that's where the weeds are sprouting.

Section by section, remove the plastic and re-spread the gravel.

The easiest weed control for gravel is a scuffle hoe or glyphosate. Pre-emergents need to be applied at exactly the right time, and are prone to being washed down too deep to prevent sprouting if there is a heavy rain, or there isn't enough rain to get them into the right soil layer.

The other two methods are applied to the active weeds.