1st Id check the servo then the rx .. a lot more info would help,make model and servo radio system so on.
servo tester for servo with a arm on it and your finger as some resistance
rx test id use known good servos and have a open area you can see rx at a distance as in radios max distance..I use a piece of sturdy wire attached to servo arm(horn) and a piece of colorful tape as flag on wires end