With the receiver using a two-key power scheme, and the sony remote only having a single power key, if the receiver was in the same power state as the code you test, it would seem no code had worked. And the volume keys may have had the tv volume instead of the stereo initially, Doesn't mean it has to stay that way. Test ALL keys, not just power and volume.

When testing codes, test the code with stereo both on and when its off. You WILL NOT find a single code that does both on & off, sorry.