You can console in to the AP and watch it boot up to verify you are getting full power (which you should). From there, you need to check your config on the IAP, but you will only get 800Mbps on 2.4Ghz with 40MHz channels and a 4x4 client (which you likely don't have). 2.4Ghz should ONLY be running at HT20 due to lack of spectrum availability in the 2.4Ghz space. You would have to likely explicitly enable 40Mhz in the 2.4Ghz radio.
Note you will never get max rates in 2.4Ghz unless inside a faraday cage, there's just too much interference.
What are you seeing at 5Ghz?