What was found
CABIN ALTITUDE HIGH WARNING MESSAGE AT 11000 FT, RAN QRH & RETURNED TO FIELD. (FLIGHT 3973D) ON INITIAL NOTICE OF CABIN ALTITUDE HIGH WARNING WHILE REACHING ALTITUDE, VERIFIED WITH CREW THAT PRESSURIZATION CONTROL PANELS MODE SWITCH WAS IN MANUAL, ENSURING THAT PLANE WOULD NOT AUTO PRESSURIZE WHEN REACHING ALTITUDE. ALSO VERIFIED THAT ON 12/23/2025 CAMP ITEM 31419919 THE PAX DOOR SEAL WAS CHANGED & PRESSURIZATION CHK HAD PASSED. WITH THIS BEING 1ST FLIGHT OF THE DAY, SUSPECT THAT MX FROM THE PREVIOUS DOOR SEAL CHANGE HAD LEFT MODE SWITCH IN MANUAL MODE. DUE TO THESE FINDINGS PERFORMED A PRESSURIZATION CHK IAW AMM 21-31-00 AS WELL AS LEAK CHECK OF PAX DOOR SEAL WITH OPS CHK OF PRESSURIZATION SYS & LEAK CHKD OF PAX DOOR SEAL GOOD. ACFT OKAY FOR CONTINUED SERVICE.