Could this be the reason why?
https://www.iberia.com/es/faqs/iberiaplus/Avios/
What do I do if I'm missing some Avios or Elite Points?- Flights operated or sold by the Iberia Group, American Airlines, British Airways, Malaysian Airlines, Qatar Airways and Sri Lankan Airlines: You can manage through iberia.com under My Iberia/Avios and Elite Points/ Non-recorded Avios.
- Other airlines associated with the programme: You will need to send the boarding card image and a copy of the electronic ticket through form.
Only some airlines work through the regular "Non-recorded Avios" form where you just enter flight details/ticket number, etc. and CX is not one of them. You have to go through the "mailbox" form where you send them the boarding card and e-ticket, like an email.