My shower has a fiberglass floor. I can't get it clean. Suggestions

Have you tried vinegar? That is always my go to for cleaning, especially soapy stuff.

you can paint it. There are all kinds of plastic paints that you can use in the shower area. Your local hardware store know doubt has some.

Easy Off No Fume Oven Cleaner in the BLUE can. Spray it on and let it liquefy. May need some scrubbing. Wear rubber gloves. Rinse well. Works on enamel, porcelain, and fiber glass.

A HAND HELD STEAM CLEANER WORKS WONDERS GOT ONE ON AMAZON

I love Bar Keepers Friend, along with a magic eraser. Works wonders!

Try spraying on Kaboom spray cleaner, double with baking sofa and borax and scrub with dampened Magic Eraser, generic ok

Baking soda and lemons. I throw a liberal amount of baking soda on my tub and scrub with half a lemon. We have red rust stains and I have gotten them completely out that way then rinse with vinegar then water.