I understand that you are having some issues with your Slingbox PRO HD since you are not able to get the HD channels.
The main issue seems to be that even though you are able to change channels, you are not able to get the HD channels. Most of the times, this issue is related to the resolution running on your set top box. Keep in mind that the Slingbox PRO HD will stream the TV signal if it runs on 1080i. If the set top box runs on 1080p, you will not get the signal.
For further details, make sure to check the following link.
You can also check the following link in order to test if the IR Blasters are working in a proper way.