Unable to confirm my identity on Facebook...

For some reason that I don't understand, Facebook asks me to confirm my identity.

Since I didn't specify a phone number on my account, Facebook gives me just one default option - "Confirm your identity on another computer: Chrome for Windows 10 (April 7 at 3:31pm)". However, I've only been using Facebook on a single computer (and I do use Chrome for Windows 10 on this computer), so I have no idea which "another" computer Facebook is asking me to verify my identity on.

Then there's a "confirm your identity another way" link, and when I press it I get an option to "Upload a photo ID". So I uploaded an image of my passport, but I received an email from Facebook saying "It looks like you didn't attach a valid form of identification to your request. We can't verify your account until you submit a copy of a valid form of ID."

So I'm stuck. I don't have any "another" computer and the guys at Facebook don't seem to accept my passport image. Any idea?

Thanks