Don't worry! Our payment processor is pretty strict with its requirements, so most of the time your file was in the wrong format or low quality and nothing more.
If you were not verified on your first attempt, you will need to start the verification process one more time.
Usually, it means that you will be asked to add more data in Step #3. Such as:
For the US, you’ll need your full SSN or the scan of your ID document.
For other countries, you’ll need a scan of your ID document.
Tip: If you are required to upload the scan of your ID document, it's better to upload a scan of your passport!