I am facing the below error
Exception Details: Update failed. First exception on row 0 with id *************; first error: TEMPLATE_NOT_FOUND, The record couldn't be saved because it triggered an email alert that failed. Please contact salesforce.com Customer Support.: 
The scenario is that we have a WF Rule on the Invoice object which fires the Email Alert after Registration. The Invoice Template is a VF Page. I researched for it and most of the folks suggest checking the permissions of the fields referenced in the Email template. I do that but still, I am getting the same error.
It's the second time I am facing this particular issue. The first time it was resolved by giving permission to a new field added on the Invoice object. But this time it happens suddenly without adding any new field.
Please suggest a way to resolve it Thanks.