IMHO, Mastech is one of the lower quality meters and I am never surprised when I hear of one of them having a problem. If it is only one month old, take it back for warranty or a refund. If you can I would suggest you consider buying another brand, Uni-Trend, Fluke, Brymen, Digitek, Agilent, Amprobe, BK Precision, Hioki, are just some examples of meters I would trust over ANY Mastech.
Sorry you haven't had any help but the answer really is: One month old and not working? Take it back.