Template is being sent using the wrong parameters. Content API templates must be sent with a Content Template sid starting with HX and include a Messaging Service. Templates created using the Legacy System through Templates API or the WA Templates Console UI must be sent with a body string.
Their requested body does not match an approved template.
Possible Solutions
Double check your body string parameter to make sure it matches exactly with the approved template. New lines or blank characters may cause an issue.
If the template was created with Content API or Content Editor. Validate that you are sending templates with the right parameters.