AGOL Reader - WinError 10061 - target machine actively refused connection

I have a workspace that runs in Workbench, but has issues in Server.

I have tried reading both:

1. Private data (via the Esri ArcGIS Online (AGOL) Feature Service Reader), as well as
2. Publicly available Living Atlas data (via the Esri ArcGIS Server Feature Service Reader)

The error messages differ slightly but are largely the same. The full text of the error message (for the publicly available Living Atlas data) is:

ArcGIS Feature Service Reader: Could not connect to server. Check that you are connected to the internet and that no firewall is blocking outbound connections. The error was 'HTTPSConnectionPool(host='services5.arcgis.com', port=443): Max retries exceeded with url: /4LKAHwqnBooVDUlX/arcgis/rest/services/ParkBoundaries/FeatureServer?f=json (Caused by NewConnectionError('<urllib3.connection.VerifiedHTTPSConnection object at 0x050672B0>: Failed to establish a new connection: [WinError 10061] No connection could be made because the target machine actively refused it'))'

Any ideas on how to fix this error?