HI Mariel! It's likely because you're on an iPad, which we don't support.
That looks Safari-ish, but if it's a default iPad browser and not Safari, and you can use Safari or another standard browser on your iPad (like Chrome) that may instead work. Can't promise that, though.
Oh, and also, just in case, note browser extensions or settings can interfere, too, so I'd check into that.
You need to, instead of an iPad or iPhone, use a Desktop or laptop with a standard browser to ensure the challenge's will work.