Unexpected token '<', "<html> <h"... is not valid JSON error

We’re getting a new error on one of workflows that we have not changed anything on. The error states: Unexpected token '<', "<html> <h"... is not valid JSON

Does anyone know what this error means and/or what it can be related to? I don’t know why this error started showing randomly but we have made no changes to the workflow @Gaurav Chadha