Send email template "permission denied to access the api"

Send email template "permission denied to access the api"

Hello,

Per the title, I'm trying to send a Zoho CRM Email template based on the advice given here: https://help.zoho.com/portal/en/community/topic/specify-an-email-template-when-sending-emails-in-custom-functions (I'd prefer to send right from Deluge but it seems I'm not alone).

So I have it all set up, but when I go to debug it (or even execute it without debug on), it is telling me that
Zoho CRM says "permission denied to access the api"
Seems cryptic. Any idea whats going on? I've attached screen shots for context, and I've confirmed the efficacy of the connection being used.