Lipo repair

[auto2]

i have a 4s 3700 i got from mike that says anyrc.com on it that has a strange proble,
everything seems normal.pack is hard and flat,charges corrctlly and is in balance butit has no power at all. if buggy is geared for 40 mph with this pack it will go 10mph full throttle. wont even rev up enough to have trouble making full speed turns on the street it is that slow. what you think?