Are you in the Fort Lauderdale area? If so, I graduated from Stranahan back in '85 & someone I went to school with is a roofing contractor - they can come out & take a look no charge to see exactly what your problem is. PS to Timothy: zero chance of snow... LoL
If your only issue is a rige cut that is too small & foam type ridge vent, then this can be overcome fairly easy (depending on your level of ability, of course).
One question before we go too much further is in regards to what your contract states. If you only have "add ridge vent" then in the basic sense of the contract you've been fulfiilled in product (but not exactly in process if the gap is too short & only cut on one side).
Knowing construction in South Florida, the pitch of your roof is probably around a 6:12 which is an easy walk, but makes the eaves harder to get all the way into for a perper check of how your insulation is stuffed (but you should be able to see if there are any baffles in place).
If you decide to do the ridge vent yourself, get some 3 Tab shingles (typically 33 linear ft. per bundle) in the matching color & either the Cobra II or Cobra III (the 3 version has nails snapped into the plastic, the 2 version needs a separate purchase).
Snap a chalk line 1" down from each side of the ridge center (tap in a nail on one end if doing a solo job) & then set a circ saw just deep enough to cut the decking but not too deep that you penetrate the rafters. Rip out the decking, then nail in the ridge vent & add shingles over this.
NOTE I like to stop cutting the roof deck by around 6" or so on the ends of the ridge vent to privent any intrusion of water from these ends.