Mysql AFTER UPDATE trigger with IF-THEN condition, but no data insertion

Hi There, I created the following AFTER UPDATE trigger on the table manage_transaction using IF-THEN condition in order to insert the specific data into the table manage_site_income_details BUT, neither a single row is inserted into manage_site_income_details nor any error encounters. However, I modified my IF-THEN condition many times, but no success. Please help me figure out the issue.

DROP TRIGGER IF EXISTS
        `upon_subscription_payment`;
CREATE DEFINER = `test-db-ru-admin`@`%` TRIGGER `upon_subscription_payment` 
AFTER UPDATE
    ON
        `manage_transaction` 
FOR EACH ROW 
    IF 
       OLD.about LIKE 'SUB' AND NEW.status = 'Completed' 
    THEN
    INSERT INTO 
                manage_site_income_details
    VALUES(
        NULL,
        OLD.t_id,
        OLD.txn_id,
        'SUB_Fee',
        OLD.fee,
        NOW());
    END IF