Trust you're having a nice day.

I want to get Clarifications on few misconceptions.

Our business has an existing ERP system internally we use for invoicing, which is designed to support us across Africa. As to this I presume we should just require the service of an APP. On the FIRS logon the MBS default APP is what we are connected to and we have the necessary credentials. We've started integration with these credentila to Validate Payload, Create a QR Code and Sign Invoice, all of these have successfully integrated.
Now the transmission seems to be an issue as we keep getting the error below

{
    "code": 403,
    "data": null,
    "message": "error has occurred",
    "error": {
        "id": "9ed92c56-f9d2-41b3-9798-123148ae99aa",
        "handler": "entity_actions",
        "public_message": "access denied. user does not have access to this resource"
    }
}

And we get this particular error when we try to hit certain endpoints too like
a. SearchEntitty Endpoint
b. GetEntity Endpoint
c. LookupWithIRN
d. Transmit endpoint e.t.c...

Are we getting a flow wrong here as to the transmission, or we are not fully registered ?

Please also note that our ERP system has been used to support Fiscalisation with African Countries that have automated their Tax Payment system, and it's been effective