Iberia won't let me check-in online

I have booked tickets from Madrid to Santiago with Iberia Express, and on my ticket confirmation - not a ticket - it says I need to check-in online at iberia.com with last name, booking ref and origin of flight. I have tried this, several times, both on iberia.com and iberiaexpress.com, but each time I get this message: The characteristics of your booking mean you cannot check in online.

Is this something I should worry about? Something I need to fix before I go? I do have very little margin for delays between my flight to Madrid T1 and out again from T4, and I need to get through security again at T4, so I need this to run smoothly. If I print the confirmation and use the check-in machines at T4, will that be okay? Has anyone had this message? I was hoping to be able to check in both flights both ways before I go so I can just take my hand luggage size pack and move from gate to gate. Grateful for any help.

Oookay, so this is one instance where I have since answered my own question and could have removed the post, but I thought I'd post the solution instead:

Turns out with my ticket (possibly all tickets?) I can only check-in less than 24 hours before the flight! So the messages saying they could not find my booking, that my info was invalid, that there were unforeseen problems etc should not be a problem on the day before I leave, according to the very nice man at the help desk. So I need to print the receipt with the barcode and take it with me, check-in online with passport number etc on the day before the outbound flight, and use the barcode from the receipt at the self-service machine at Santiago airport before going home. Problem solved, panic over!