Can someone help me fix this “communication error” with the Global Trading System?

      Can someone help me fix this “communication error” with the Global Trading System?

      So I’m playing Pokemon Diamond and I’m trying to use the GTS with a friend in order to evolve my Graveler. My wifi connection uses WEP security and everything, and the wifi tests the DS performs on the connection always proves successful. But every time I seek on the GTS and tap on a person to trade with, I always get a “Connection error...” code. Any ideas? My DS is not hacked or cheated. It’s a new 3DS XL.