2910375 - Error: "HTTP 401 - Unauthorized"

I receive the error HTTP 401 - Unauthorized for HTTP requests sent from Managed Gateway for Spend&Network to the SAP ERP system. The error is received for the below scenarios:

• In the Managed Gateway for Spend&Network Transaction Tracker, the documents are failing with the error message: Fault response received from: ANxxxxxxxxxxx for: ANxxxxxxxxxxx with Status: FAILED and ErrorResponse: Unauthorized. 
• While testing the connection in the Managed Gateway for Spend&Network Connectivity Tool, I receive the error message: Error: - HTTP 401 - Authorization denied for the credentials provided for basic authentication. Incase of Certificate authentication, user associated to the Managed Gateway for Spend&Network public certificate is not authorized on the target server.
• The threads in the Internet Communication Manager (ICM) related to the Managed Gateway for Spend&Network connection returns HTTP/1.1 401 Unauthorized.

• Managed Gateway for Spend&Network
• SAP ERP Central Component (ECC)
• SAP S/4HANA

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