How long have you had an Iberia account? The two reason for the above message are usually that you have not had the account running with Iberia for the requisite 90 days and the address on the Iberia side needs to be valid (you can create an Iberia account without fully giving an address). You also need more 1 or more Avios in the account.

In my version of that screen the 3 boxes are not greyed out.