As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON DEPARTURE, LANDING GEAR WOULD NOT RETRACT. ALL GREEN LIGHTS STAYED ON AND ALL RED LIGHTS WERE ON. IT FELT LIKE THE GEAR REMAINED IN THE DOWN POSITION WITH NO MOVEMENT. RETURNED TO RNO. REPLACED LEFT GEAR UPLOCK A SYSTEM PROX SWITCH IAW 32-61-01. OPS CHECKS GOOD.