We can never check in on-line when departing AMS through the KLM website, but have been able using the Air France website leaving CDG or intra-Europe AF connecting flight. The AMS issue is not associated with the enhanced security selection, but probably more due to traveling on green card requiring manual processing (though family on US passports seem to have the same issue at AMS). So may be a system issue or related to the country you fly out of in addition to the possibility of SSSS selection.