Others are reporting this, so it would seem there's a temprorary fault on the site.
However, which device are you using? If the app or mobile browser, can you, switch if you can to a PC/laptop, and try from there.
Switch to Chrome it works best with eBay.
I'm on a laptop using Chrome, and had no problem during that period to upload and add photos to my listing.
@chalet_etoille