I have found that you can use the BA website to obtain Iberia.com record locators. Try this:

Look up your AA record locator on BA.com and make a note of the BA record locator number indicated for Iberia flights. BA and IB share record locators so you should not have any issue, the BA site will show your IB flights.

take the BA record locator and input this on IB website.

Worked for me on IB LHR - MAD - ORD

Good luck