We send out invitations when the platform you work with includes you for access. Different platforms have different conditions for registration. If you were expecting to receive an invitation to register and you haven't been able to, then please check your email for an invitation (including checking in your junk/spam folder). If you aren't able to find an invitation then it's most likely that you haven't been included yet.
We receive regular updates from the platforms we work with, so you may be included, just in the next update. When you are included for the first time, you can expect to receive an invitation from us via email.
If you think you have been included and are having a problem then we'd be happy to double-check. Just get in touch and let us know!