ok you should first enable event_scheduler using your mysql command line:SET GLOBAL event_scheduler = ON;
now lets create your schedule :
-you want to update a column if the condition of comparing two other columns are met.i guess this syntax will handle the problem:
CREATE EVENT test_event_04 ON SCHEDULE EVERY 1 DAY STARTS CURRENT_TIMESTAMP
DO UPDATE table_name SET STATUS='expired' WHERE CURDATE()>date_expiration AND proof_of_payment IS NULL
just remember to change table_name to your real table name
the schedule will run every day once created (EVERY 1 DAY STARTS CURRENT_TIMESTAMP )