Director Notifications - Argument missing


I’m using this version of Icinga and Director:
Icinga 2 version: 2.11.2-1
Director version 1.7.2

My Director is set up this way for notifications:

However, when I send out a test notification I get this error message:

"Required parameter 'LONGDATETIME' is missing."

Full log:

[2020-01-07 09:55:59 -0500] warning/PluginNotificationTask: Notification command for checkable '' and notification '!Basic notify - Hosts' (PID: 25401, arguments: '/etc/icinga2/scripts/') terminated with exit code 1, output: Required parameter 'LONGDATETIME' is missing.

Required parameters:
  -d LONGDATETIME ($icinga.long_date_time$)
  -l HOSTNAME ($$)
  -n HOSTDISPLAYNAME ($host.display_name$)
  -o HOSTOUTPUT ($host.output$)
  -r USEREMAIL ($$)
  -s HOSTSTATE ($host.state$)
  -t NOTIFICATIONTYPE ($notification.type$)

Optional parameters:
  -4 HOSTADDRESS ($address$)
  -6 HOSTADDRESS6 ($address6$)
  -c NOTIFICATIONCOMMENT ($notification.comment$)
  -i ICINGAWEB2URL ($notification_icingaweb2url$, Default: unset)
  -f MAILFROM ($notification_mailfrom$, requires GNU mailutils (Debian/Ubuntu) or mailx (RHEL/SUSE))
  -v ($notification_sendtosyslog$, Default: false)

I’m not sure where else to look next - the mail notification script is in the right directory and has the correct permissions.

If I change the template to use the built in command (the External one, not the one built in Director), like this
External command shows this:

I cannot deploy because of this error:

[2020-01-07 10:15:52 -0500] information/cli: Icinga application loader (version: 2.11.2-1)
[2020-01-07 10:15:52 -0500] information/cli: Loading configuration file(s).
[2020-01-07 10:15:52 -0500] information/ConfigItem: Committing config item(s).
[2020-01-07 10:15:52 -0500] information/ApiListener: My API identity: monitoricinga.example.local
[2020-01-07 10:15:52 -0500] critical/config: Error: Validation failed for object '!Basic notify - Hosts' of type 'Notification'; Attribute 'command': Object 'mail-host-notification' of type 'NotificationCommand' does not exist.
Location: in [stage]/zones.d/master/notification_templates.conf: 2:5-2:38
[stage]/zones.d/master/notification_templates.conf(1): template Notification "All admins - Hosts" {
[stage]/zones.d/master/notification_templates.conf(2):     command = "mail-host-notification"
[stage]/zones.d/master/notification_templates.conf(3):     period = "Always"
[stage]/zones.d/master/notification_templates.conf(4):     users = [ "xxxxxxxxx" ]

I’m not sure why it complains that it doesn’t exist - the external command is loaded in fine and can be seen in the screenshot above.