SendGrid v3 Api dynamic template_id not recognised, won't send - sendgrid

Question

I am trying to send a simple password reset email that's defined in a dynamic template. I have tested the template within SendGrid and it works fine. I have copied and pasted the template_id from the website, checked and double-checked it, but trying to post this message:
{
"personalizations": [
{
"to": [
{
"email": "chairman###########.org.uk"
}
],
"dynamic_template_data": {
"firstname": "Tim",
"url": "https://localhost:5001/account/ProcessPasswordReset?id=4&code=############"
},
"send_at": 0
}
],
"from": {
"email": "membership###########.org.uk",
"name": "A Person"
},
"reply_to_list": [],
"subject": "Password Reset",
"content": [],
"template_id": "d-23a2c68a9e5349488be23299a04a9485",
"send_at": 0
}
I get the following response
{
"errors": [
{
"message": "Unless a valid template_id is provided, the content parameter is required. There must be at least one defined content block. We typically suggest both text/plain and text/html blocks are included, but only one block is required.",
"field": "content",
"help": "http://sendgrid.com/docs/API_Reference/Web_API_v3/Mail/errors.html#message.content"
}
]
}
As far as I can tell from the documentation, this is a well-formed message with a correct template_id.

Answer 1

Ok so the problem was the empty
"content": [],
This must not be sent at all if there is no content to send. Working as expected now this is removed.