These 2 boxes both use the same set of codes so you must be doing something wrong.
....I found a file for GigaBlue HD 800 Solo and does not work with my gigablue hd quad plus.
I quote from the instructions:
IMPORTANT: If you have any problems PLEASE read ALL of this file before you post a question on the forums. In particular, if you just reply that 'it doesn't work' you probably wont get any further assistance.
But I will let you off this time as long as you promise to read the latest instructions properly: Use http://placeshiftingenthusiasts.com/how-to-install-a-custom-remote-onto-the-slingbox/