Some vehicles now have a solid state relay (transistor) instead of an electromechanical one. It could be inside a computer. If it's a discrete relay, it would be in a power distribution box underhood, where the maxifuses are (40 amp and up). The lid of these boxes has a diagram showing which relays are which.
The newer vehicles use a TIPM (totally integrated power module) for smart power management instead of the old PDC (power distribution center). You may need a scan tool to read why something has been 'turned off'. It is usually to protect the circuit, i.e.- like a detected short, if the A/C compressor circuit has been disabled.
Is the compressor not coming on?