With this model of universal remote, which is just preprogrammed remote, meaning you are stuck with whatever's preset. There is no way to add missing commands.

See you receiver has a key for ON ,and another for Standby. It may respond to a toggle that does both, but that toggle won't be preset via ANY of the Sony codes. And there's no way to add it to the Sony universal you have. So one of the commands will always be missing.

The command that is preset is probably the discrete ON command, if you were testing the codes with receiver on, that discrete command would seem to do nothing since the receiver is already on. That's why when entering each code, before giving up on it, test it on your receiver with receiver both on and in standby. And test the reset of the keys for each code, with receiver on.

In the end I would dump that universal, get a least one with learning function. If you like sony, that would be the rm-vlz620. Check for the RF10, being discontinued, it's discounted, code library isn't anything, but the learning memory is huge. Or get a Harmony.