When you're done watching this video you'll know how to determine whether the company you hired to replace your garage door spring installed the right size spring on your door. You'll also learn the consequences to your garage door opener if the wrong size spring is used. If you are having a problem with your garage door spring, the 2:30 minutes you spend watching this video is time will spent.
It's also possible that the circuit breaker, fuse, or GFCI controlling the door opener circuit has tripped or burned out. If you find that other lights or electrical circuits in the garage aren't operating, this is the likely cause, and you'll need to reset the breaker or GFCI or replace the burned-out fuse. If the circuit breaker or GFCI is tripping repeatedly, it's a sign that there is a short circuit somewhere in the system—possibly even the garage door opener itself.