Make sure that your acetone is actually acetone. According to the MSDS, ABSPlus-P430 is indeed "ABS resin" so acetone smoothing should work. Some companies sell confusingly-labeled products that might be mistaken for acetone, but are actually "eco-friendly" alternatives such as 2-butoxyethanol. While these alternatives work for some of the uses for which acetone is normally used (such as cleaning or degreasing), they don't work for smoothing ABS.