WNDR4000 compatible with Window SBS 2011 Essentials?

I'm trying to set up Remote Web Access on the server. The error message is port forwarding not configured on the router--even though I did set it up. Also, it says that Remote Web Access is blocked, and that "some" routers may not work properly. I do have the latest firmware update, but it didn't help.

Any ideas?

TIA

JRY