As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURN BACK, CABIN ALT, CABIN ALTITUDE LIGHT EICAS MSG DISPLAYED OPERATIONAL AND MANUAL MODE RESTORED CABIN PRESS CABIN AUTO INOP 1 AND 2. IAW AMM 21-31-01/401. CABIN PRESSURE SELECTOR WAS REPLACED AND WAS ACCOMPLISHED CABIN PRESSURE CONTROL SYS, OPS TEST IAW TASK 21-31-00-705-001. TEST SATISFACTORY. (K)