Ok If the lights are on it means you have 12 volts.
It may wait till it calls for cool before it switches, that can take a while
or.. Even if it does not wait it can take a minute or two.. I know there are times when I wish to FORCE gas mode (Last week for examnple) Now last week I got it to work properly but either the Fridge, or I needed some work (Not sure which) on that so in the past I turned off A/C then waited,,, I knwo it took quite a while before it switched.. Then I'd tap the auto button and restore power to the other devices on that line.
(Finaly figured out you lean on the bitton for a while to force and lock)
Fridge dropped 10 degrees overnight on gas.