When using the Rest API integration method, one of the headers that must be sent with each Rest call.
One of the main headers listed that verifies the account included within the call is the X-Forte-Auth-Organization-ID header.
For this header you will need the Organization ID listed on your live or sandbox merchant account.
The header would need to be formatted as follows.
X-Forte-Auth-Organization-ID = org_{insert Organization ID}