802.11n isn't a frequency. N can work over 2.4 (just like G) or 5 GHz. The Evo doesn't have a 5GHz radio, so even if it's using N it's on the lower frequency.
Make sure your wireless router is on "N only" and not on "Mixed Mode". If on mixed mode, it will use a/b/g/n, but if on n only, will only look for n. EVO definitely does not work on 5GHz only on 2.4.