They clearly had problems with their railgun prototypes (think it got to work OK, but well, minimizing, energy reduction, lifetime etc. was still something they would need to do, so lots, and I mean lots of more money and time would have been needed).What's wierd is the USN has also appeared to drop both General Atomics' and BAE's railguns.
Not to mention a lot of newer US 'tech' has been a 'failure' (Zumwalt, lots of problems with the Ford etc.)
As for China, really hard to say but we do know they made great leaps in tech (and are ahead of the US in certain areas), professor Ma Weiming came out and even said that China were 10-20 years ahead of the US when it came to electricity tech (or something like that).
There were also some months back that electromagnetic gun that fired fire extinguisher rounds (something for fire-fighting, and yes I know it only fires a round some few kilometers at a much lower speed, but it still shows that they are definitely working on electromagnetism and can even produce civilian use equipment).
Also in general, the PLA can be very secretive about stuff it doesn't want others to know and railguns is definitely an area where they want to conceal it (I believe the PLA sees it as the future? especially to replace more traditional guns)