Zoho Flow to SendOwl API error

Zoho Flow to SendOwl API error

SendOwl is listed in the apps list of Zoho Flow.
When trying to connect through the API with valid key and secret, the error given is:
SendOwl says "HTTP Basic: Access denied"



It seems Zoho doesn't connect via HTTPS.
I've already tried using webhooks, but that doesn't allow me to get the product (name).
So unless I pay Zapier, I don't know how else to connect both.