3277937 - Upgrade to protocols [websocket] denied for resource

The following error is observed in the SAP Cloud Connector ljs_trace.log file when trying to access a backend resource: 

2022-12-09 19:30:12,351 +0000#ERROR#com.sap.core.connectivity.spi.processing.AbstractProtocolProcessor#tunnel-client-9-3#0x140d5h1f#Write operation FAILED for payload message packet with size 1,220 for client channel [id: 0xa1260c38, L:/<ip>:<port> - R:<backend host>/<ip>:<port>]. Cause: com.sap.core.connectivity.protocol.http.handlers.HttpProtocolException: Upgrade to protocols [websocket] denied for resource "/sap/bc/apc/sap/webgui_services" on system "<virtual host>:<virtual port>".In case this was a valid upgrade request, ensure to allow the upgrade in your Cloud Connector.

SAP Cloud Connector

SCC, Protocol processing error, Write operation FAILED , KBA , BC-MID-SCC , SAP Cloud Connector On-Demand/On-Premise Connectivity , Problem