Vrrp_scrpt script is not executed in keepalived

when using keepalive, it is found that the vrrp_scrpt script has not been executed. The configuration is as follows:

by configuration, when / etc/keepalived/down exists, the priority of MASTER drops to 80, but the script never triggers.

MASTER

! Configuration File for keepalived

global_defs {
   notification_email {
     root@localhost
   }
   notification_email_from keepalived@localhost
   smtp_server 127.0.0.1
   smtp_connect_timeout 30
   router_id LVS
}

vrrp_script chkdown {
    script "[[ -f /etc/keepalived/down ]] && exit 1 || exit 0"
  interval 1
  weight -20
    fall 1
    rise 1
}

vrrp_instance VI_1 {
    state MASTER
    interface ens33
    virtual_router_id 151
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 486fcd6f30e1
    }
    track_script {
chkdown
    }
    virtual_ipaddress {
        192.168.101.231/24 dev ens33 label ens33:0
    }
    debug
}

BACKUP

! Configuration File for keepalived

global_defs {
   notification_email {
     root@localhost
   }
   notification_email_from keepalived@localhost
   smtp_server 127.0.0.1
   smtp_connect_timeout 30
   router_id LVS
}

vrrp_script chkdown {
    script "[[ -f /etc/keepalived/down ]] && exit 1 || exit 0"
  interval 1
  weight -20
    fall 1
    rise 1
}

vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 151
    priority 90
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 486fcd6f30e1
    }
    track_script {
chkdown
    }
    virtual_ipaddress {
        192.168.101.231/24 dev ens33 label ens33:0
    }
    debug
}