Given the range of problems your having it sounds like there is some underlying network issue.
How is the player connected to the network wired or wireless, if wireless try connecting it temporarily via wired to your network router.
If your already on wired does the router have some sort of firewall built in that might be blocking the network traffic.
I think he's saying the phone app is a problem. I'd suggest on your phone (its android) using Skifa as your DLNA controller app and as next010 says use Serviio. It has very good support for Sony and I know from the Serviio forums they are doing further work on the SMP-N200.
Very cheap long Ethernet cable:
AmazonBasics RJ45 Cat5e Ethernet Patch Cable 50 Feet / 15.2 m: Amazon.co.uk: Computers & Accessories
What router do you have ? make and model required. Have you updated the firmware ? do you have UPNP enabled ?
Not familiar with the router, a quick google seems to suggest its a TalkTalk free router ? I think its the same one my sister had from TalkTalk, they had to buy a real router in the end.
They offer d-link routers with wifi n if you push them