Just called EK again as still not able to OLCI after the first agent said to leave it for a couple of hours.
The second agent checked and confirmed the booking is fine, all details required are completed and that it is only because OLCI is not open yet (despite receiving and SMS, e-mail and the iOS App saying that OLCI is open).
May be a local thing here in PEK so I'll try a little later.
Safe & Happy Travels
S