Hi,
there's a tool called IRScrutinizer that is very useful analyzing IR signals.
Another useful tool is MakeHex which lets you easily create complete codesets for a protocol specifications.

According to IRScrutinizer, the VOLUP code you gave is indeed RC5, device 16, function 16 and a base frequency of 36.045kHz.

The "example on/off" code seems to contain some error, but I don't see what it is at the moment. The code PEP3 generated looks okay, though and I can't see why it would not be working.

I created some codes with MakeHex; try if those are working for you:

Device Code: 16 Function: 12 (on/off)
0000 0073 0000 000B 0020 0020 0040 0040 0040 0020 0020 0020 0020 0020 0020 0020 0020 0020 0020 0040 0020 0020 0040 0020 0020 0CC5

Device Code: 16 Function: 13 (mute)
0000 0073 0000 000B 0020 0020 0040 0040 0040 0020 0020 0020 0020 0020 0020 0020 0020 0020 0020 0040 0020 0020 0040 0040 0020 0CA4

Device Code: 16 Function: 16 (vol up)
0000 0073 0000 000B 0020 0020 0040 0040 0040 0020 0020 0020 0020 0020 0020 0020 0020 0040 0040 0020 0020 0020 0020 0020 0020 0CC5

Device Code: 16 Function: 17 (vol down)
0000 0073 0000 000B 0020 0020 0040 0040 0040 0020 0020 0020 0020 0020 0020 0020 0020 0040 0040 0020 0020 0020 0020 0040 0020 0CA4

Sebastian