I have replaced my A1521 with a new DLink DIR-890L as my primary wireless router. My older Airport Extreme Base Station hopped on and exteneded DLink wifi network allowing me to network printers via Cat 5 cables. My newer Airport Express acted in kind. When I try to get the A1521 to allow me to "Add to an existing network" it announces that it can't locate any base stations. I don't understand why the newest apple wifi tech I own will not join the same DLink wifi network the older Apple tech hopped onto. Please help. I need the network ports on the A1521 for other non-wifi hardware. Hard reset has not fixed the issue.