Plastics can be tricky, especially black plastics.

Soap and water was a good start, did you use dish soap or hand soap?

A good trick is to use a hair dryer to warm the plastic, it causes anything permeated to rise and obviously the plastic to expand, on a measurement we don’t even notice that allows space for a nice warm dish soap to get in and clean try a soft bristle brush, or toothbrush.

Dish soap works best because it’s both hydrophilic and hydrophobic.

It’s also great for say a preowned car you’ve just bought and plan on detailing yourself as it really takes the paint back to basics so you know what you’re working with!

Don’t use nail varnish remover, don’t use car polish, ISO alcohol may work but I’d do a minuscule spot test to make sure it doesn’t haze the finish.

Use circular motions and be patient :)