This happens more than you'd expect, and it's usually because of something simple like:

Unclear documents

The pictures of your documents you uploaded were blurry, cut off, obscured, or not in colour.

Information mismatch

The details on your documents (like your name or address) didn't match the information on your account.

Expired ID

The identification document you provided is out of date.

Invalid documents

The type of document or proof of address you provided was not on our approved list.

Poor selfie

The selfie you took was blurry, too dark, or didn't closely match the photo on your ID.

The good news is you can try again at any time.

You should have received an email with the specific reason for the rejection, so keep that in mind when you repeat the process.