Most of the templates are getting rejected because the characters exceed the actual character limits.

These are the character limits applied to message templates:

Header

·        Caption is limited to 256 characters, text is limited to 60 characters.

Body

·        For media message templates, these cannot exceed 1024 characters, while standard templates are limited to 4096 characters.

·        When requesting the template the body is restricted to 1024 characters (parameters {{n}} count as 1 character).

Footer 

·        Limited to 60 characters Buttons 

·        Caption is limited to 20 characters, while payload for the quick replies is 256 characters.