I was able to remove the cover and put it in the washing machine. There might be instructions online on how to do this.

I would try to google the instructions and see if you can find cleaning instructions.

I’d email the manufacturer to ask direct.

I always thought you could remove these to pop in the machine and wash.
Maybe have a look at the bottom and back and see if you can take it off as it’ll be so much easier.

Depending on the model you can hopefully pull it apart and remove the material/canvas parts and give them a good scrub and soak and may even be able to go through the washing machine. I always did this with prams and high chairs.

Also maybe do a search; there might be some tips on forums. The product site might also have some handy tips.

I always use a very gentle washing detergent to spot clean fabric.

If the material is detachable I’d try a stain remover, and to soak if it’s an option. If not, spot clean with a little remover spray and blot away.

I’d try a mild dishwashing detergent and warm water for the material and see if that helps take the mark off.