My first go would be jif and a good scoure sponge

Bleach it – or domestos. Let it soak. Scrub with a soft scourer to remove ring. Don’t leave dirty water to sit

I use jif ,it’s cheap and works wonders on alot of surfaces.

I use bleach – hospital grade and it gets the rings off our bathtub. I need to use a bit of elbow grease for some of the edges of the rings though.

if it didn’t bleach off then you need some gritty paste to help. gumption or jif on a scourer.

I second Gumption as it is good for stubborn stains.

Gumption us great for this type of thing.