While performing an Outbound connectivity test using Connectivity Tool in SAP Integration Suite, managed gateway for spend management and SAP Business Network, the below error is returned:

Error: Managed Gateway for Spend&Network unable to connect to your server as it responded with an Error - HTTP 403 - Server cannot serve the HTTP request as the requested user doesn't have necessary ACL or permissions on the target server

The cause for the issue can be any of the below:

1. The Managed Gateway for Spend&Network integration User may lack the necessary authorizations in order for it to be valid for use.
2. The SAP Cloud Connector Subaccount linked to your Managed Gateway for Spend&Network account is not configured correctly.
3. The SICF path to which the connectivity test points in your ERP exists, but is not active.

1. Ensure that the Username used in the Connection has been assigned all the necessary authorizations in your ERP system as per the Managed Gateway for Spend&Network Installation guide section Defining authorizations.
2. Ensure the Cloud Connector Subaccount is connected properly and has correct URL path as /sap/ as detailed in SAP KBA How to identify cloud connector configuration issues for SAP Integration Suite, managed gateway for spend management and SAP Business Network specific scenarios - SAP Integration Suite, managed gateway for spend management and SAP Business Network.
3. In your ERP, go to Tcode SICF and ensure that the service under path /default_host/sap/bc/srt/xip/sap/documentstatusupdaterequest_as/<Client>/documentstatusupdaterequest_as/ is active.

For additional information, please refer to SAP Article [CIG] HTTP 403 Forbidden
For a more detailed guide with step-by-step instructions to resolve the 403 issue, please refer to the link Checking the endpoint in the ERP - Troubleshooting CIG Connection issues - Guided Answers

SAP Integration Suite Managed Gateway > Managed Gateway for Procurement