When did it work, when did it stop working, and what did you do in between?
Not long ago, the Espressif Corp updated the Arduino core and some libraries, which broke a lot of existing code.
If you updated your setup and recompiled the code, that may explain the problem.
Otherwise, suspect a problem with the wiring or servo power supply, which you did not adequately describe. Please post a wiring diagram, with all pins, parts and connections clearly identified and labeled. Hand drawn is fine.