Clean black marks off white ceramic tile.

Here are several suggestions, see if any will help you:

https://wd40.co.uk/tips-and-tricks/how-to-remove-scuff-marks-from-ceramic-tile-floors/

I would try Magic Eraser.

Try a magic eraser

Mr Clean Magic Eraser will remove it

They may be scratches rather than black marks. After cleaning with a magic eraser, if they persist then try restoring by rubbing in baking soda that is barely damp. I had to do that with the marks on my kitchen sink.

I would try Magic Eraser, it should come right off.

Thank you. Will definitely try today.

A pencil eraser can be used on any type of tile floor to remove the mark. Hold the eraser to the floor at a 45-degree angle, and sweep it back and forth across the mark. Because the black mark is not a stain and has not penetrated the surface of the tile, the eraser can usually rub or move the mark from the surface of the floor. The mark often gets rolled up with the small pieces of eraser, allowing you to sweep it up. If any mark remains, or if there is residue from the eraser, wash the floor a second time to remove it.

Deposits from the crutches pads,yes?

Goo Off from Dollar store.

Hi Diane, Make a smooth paste by mixing about 2 tablespoons of baking soda and warm water. Make sure the paste is not too runny. Now take a soft cloth and gently rub your baking soda paste on the marked areas. Once the scuff marks are removed, use a clean damp cloth to wipe the area and let it dry

Hello. A magic eraser moistened with soapy water might be your best friend.

Have you tried a "Magic Eraser"?

Magic eraser

Hello there,

Try Magic Rubber! or Barkeeper Friend with a little water.

You can use Acetone, the kind you buy in the Hardware store, not nail polish remover.

Hi, have you tried rubbing the scuffs with WD40 on a soft cloth?

I use Krud Kutter very good for tile marks

You could try Barkeeper friend or WD 40 or a Pencil Rubber.