Trying to go directly to Iberia (and not yet through a third party legal firm that takes a fee of compensation awarded) to file for a cancelled flight, then delay and rebooking on Iberia earlier this month. We did get a "certification of cancellation" issued but now trying to file for compensation of cancellation, delay, or change of schedule the embedded customer service request form will not accept confirmed data.
Tried phoning customer service, but of course they can't help. Ended up using the Spanish govt complaint form for EC261 and tried to explain they won't even accept our documentation to start a claim. Not sure if this will work, and will likely end up going through a legal firm.
I'll update as this goes through the process but it could take months, I know.