Trigger is failing with no errors at all, why?
Try with: 

USE `veeva_new`;

DELIMITER $$

DROP TRIGGER IF EXISTS veeva_new.userterritory_ai$$
USE `veeva_new`$$
CREATE DEFINER=`root`@`localhost` TRIGGER `veeva_new`.`userterritory_ai` AFTER INSERT ON `userterritory` FOR EACH ROW
BEGIN
    # [ VARIABLES DECLARATION ]
    DECLARE vUserID VARCHAR(18) DEFAULT '';
    DECLARE vTerritoriRep VARCHAR(45) DEFAULT '';
    DECLARE vTerrytoriLastMod DATETIME DEFAULT '0000-00-00 00:00:00';
    # [ VARIABLES ASIGNATION ]
    SET vUserID         =NEW.userid;
    SET vTerritoriRep   =(select IFNULL(reps.territories_id,'N/A') from pdone.reps where reps.veeva_rep_id=vUserID LIMIT 0,1);
    SET vTerrytoriLastMod=(SELECT reps.lastSyncAt FROM pdone.reps WHERE reps.veeva_rep_id=vUserID LIMIT 0,1);

IF (NEW.territoryid != vTerritoriRep) THEN
    UPDATE pdone.reps 
    SET reps.territories_id = NEW.territoryid, 
        reps.lastSyncAt = IF(NOW()&gt;vTerrytoriLastMod,NOW(),reps.lastSyncAt), 
        reps.updatedAt=now() 
    WHERE reps.veeva_rep_id=vUserID; 
END IF;

END$$
DELIMITER ;


Assuming veeva_rep_id = NEW.userid (from userterritory).

This will update reps.territories_id when the NEW.territoryid is updated, reps.lastSyncAt when reps.lastSyncAt be greater than @TerritoryLastMod and reps.updatedAt = now(), current timestamp.