Ah... I was trying to do
Program Effective Function Code (EFC) for a single device using those mute and power codes you said (00057 and 00053), and it wasn't working.
But, I just realized that since I set the TV part of the remote to my new tv using 991, and the power and mute buttons work there (when I press TV on the remote), what I should be trying to do is
Copy one key to another device.
...
Ok yeah, I used that just now and was able to copy the mute button over. But the power button won't copy over to the "C" button (it's a little red button with a C on it). I assume that's because the power button is like a "special" button that you can't copy that way.
So I'm going to try to program the TV C button to also be a power button (00053), and then try to copy that C button over to CBL
...yup, got 00053 onto the C button for TV
...But it won't copy over. Neither the power button, nor the new power button I made will copy over. Instead of 2 blinks at the end of the process, I just get 1 solid light.
...
Ok, so now I tried
Assign Effective Function Code (EFC) from another device with 00053 and it worked! woot!