Error message with HTML notifications in Incidents

Good morning Experts,

I have been tasked with sending out some alerts and HTML notifications when an SLA reaches certain times.

Goal: Create Service Level Targets (SLT) for incidents

This SLT (process target) will apply to the incident when an incident is created with varies level of impact

1- Critical Impact (2 hours to resolve)
2- High Impact (4 hours to resolve)
3- Low Impact (168 hours or 7 days to resolve)
The results that we would like to see is that the incident ticket is consistently being worked on and meeting the SLA according to the impact.

Some of tasks that we would like to accomplish are as follows:

Create a new SLA that will start with any new incident ticket is created ex.. (Base Monitoring SLA for IT services)
Alerts vs Notifications
How to send out the best option between the alerts or notifications
Notify the assignment group/assignee when the SLT has reached 25%,50%,75% and then notify the incident manager when it is breached.
So to accomplish the first set of goals I created alerts for each of the percentages (25,50,75).

So this is where I get lost:

Create the message
Message number should be the same as the message
Language Code: en
Class: alert
Message Number: message name
Notification Definition
Msg Class: HTML Template
Msg No: Name of the message
Arguments: jscall( "htmlemailtemplates.getMailBody", "name of the HTML notification", $L.file, $L.file.save)
Condition: ??
Format: ??
Notify Method: email
Recipient: who you want to receive email
I often get this error message back with the HTML notification all of the HTML tags

Message HTML Template-1 Could not be found: