It sounds like the payment process is finally working.
On the application, did anybody include their middle name in the "First Name" field?
The PDF guide says that the "information MUST be correct and same to your passport" but is ambiguous on whether this should be all given names. To match the passport and GE card, I assume all given names should be listed.
Could someone provide data points if they're available? If not, I can contact the NIA via the web form.