The recommended ESC should be OK with that motor provided you are also using the recommended prop. No need for a 25-30 Amp ESC for this setup. However, running a larger than recommended prop will draw more current which could damage the 8A ESC.

A few questions:

If you go through the ESC setup procedure, do you hear the beeps described in the instructions? Note that you will not hear any beeps unless the motor is connected to the ESC (the ESC uses the motor as its speaker).

Did the ESC ever work properly? Did the motor run properly at first but has now stopped running?

Do the servos work properly, or have they stopped working, too?

Have you double checked all your connectors?

If you did any soldering of the connections, are you sure you soldered properly?

Did you ever connect the battery to the ESC backwards (reverse the red and black power connections)? That can instantly damage an ESC.

- Jeff