Whilst video is streaming on SlingPlayer on your laptop, find out what StreamType is reported on the status screen by pressing Shift-Alt-I (the letter I for Indigo). It should say "TCP" not "SNATT". My guess is it will say SNATT.
SlingCatcher does not support SNATT, so it will not be able to find a path through the internet and Sling's systems to your Router and onwards to your Slingbox. The SlingPlayer software cleverly downgrades from TCP to SNATT when there are problems with internet routing or Sling's systems.
It could be that your Chinese ISP has started blocking comms to port 5001? I believe that SNATT finds an alternate route. However, as said above, SlingCatcher does not use SNATT.
Alternatively, perhaps Sling have auto-updated the HDPro firmware and broken the "TCP" stream used by SlingCatcher