KLM Flying Dutchman - Internet check-in for KL flight on CO ticket?

I'll be travelling MAD-AMS on a CO e-ticket in a couple of weeks. Will I be able to use KLM's internet check-in for it? I've tried using the reservation check feature on KLM's webpage buy I get an error message. The reservation number I'm entering is the one given to me by CO for the entire MEX-EWR-MAD-AMS-IAH-MEX trip. Should I call CO and ask them to give me a KL confirmation number just for the MAD-AMS leg?

Thanks in advance.

Are you making a stopover in MAD? - if not you should be able to check in in MEX all the way to AMS.

The confirmation code of CO does not apply to KLM. You should call KLM and ask for the code as they see it.

Thanks.

I'm staying in Spain for a few days before continuing on to AMS.

I'll call KL and ask them for their confirmation number.

I called KL and they gave me their confirmation code, but it didn't work either.

What worked, however, was entering my CO confirmation code followed by the suffix "/CO". Now I just hope I can do the internet check-in when the time comes.