It is 2021. You can’t just say “website” or “Firefox”. Those are just words without any meaning. They don’t tell us what website it is, what browsers or operating systems that site supports. “Firefox” doesn’t tell us what version you have, what extensions are installed, what security settings are enabled, what ad-blockers are running. Any single one of those aspects, or your unique combination thereof, could break this.
If you need to interface to the hardware and operating system, it would be best to use Safari. If you have any extensions or ad-blockers installed, you will need to disable them. Once you complete this verification step, you can then use the site with whatever browser you want.
However, I strongly encourage you not to use this site. You are opening yourself up to having your image used in marketing, AI databases, crime databases, stock art, identity theft, and literally more different types of fraud than I can even think of. This is bad, bad news.