Good day!

You can put the servo in the throttle position in the rx and test it there to see if it works. This will tell you if it is the servo or the rx that is not working. If it is the servo, take the bottom of it and with a multimeter test each wire from the conector to where it is soldered on the board for continuity. Sometimes a wire can brake inside without the outer cover failing or the wire can come off the board where it is soldered.