When you have more than 1 trigger, Marketo reads it as "Or" even when you've selected "Use ALL". That's why Advanced is disabled. I would suggest using 2 campaigns, and set it up this way:
Trigger 1: Visits Web Page > Web Page contains www.ourwebsitedomain.com/services
Filter 2: Visited Web Page > Web Page contains www.ourwebsitedomain.com/contact
Trigger 2: Visits Web Page > Web Page contains www.ourwebsitedomain.com/contact
Filter 1: Visited Web Page > Web Page contains www.ourwebsitedomain.com/services
That works, thanks Christa.
Follow up question: if I add a time constraint to the trigger and the filter where "Date of Activity is in past 1 day," will that successfully filter out leads that visit a services page one day, and then a contact page a couple months later, for example?