As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: AT ABOUT 50 KNOTS ON TAKE OFF ROLL OUT A "AMBER SMOKE LAVATORY" MESSAGE. DISCONTINUED TAKE OFF LIGHT WENT OUT AFTER A FEW MINUTES 3L LAVATORY SMOKE DETECTOR COULDN'T BE RESET. RESET LAVATORY 3L SMOKE DETECTOR ACCOMPLISHED LAVATORY SMOKE DETECTOR OPERATIONS TEST NO FAULTS DETECTED REF AMM 26-13-00-710-801.