Is it a regular boat ramp? Do you know of or have seen other boats launched & retrieved there? Is the water high enough to float your boat? I'm able to get my 26S in and out of regular state park ramps, your 17' supposedly will float in 1.42 feet of water.
Stupid question, are you sure you got all the tie-down straps off before your attempted launch... I've forgotten one time over the years, especially when rushing if the ramp is busy, seen others do it too.
Was your swing keel pulled up all the way to clear the trailer?