Unable to connect to the Qlik Sense engine is commonly caused by idle session timeouts (20+ minutes), blocked WebSocket traffic, or stopped Qlik Sense services. Other factors include network device timeouts, misconfigured virtual proxies, or expired security certificates. Immediate fixes include refreshing the browser, checking service status, or white-listing IP addresses in the QMC.
Key Reasons for Qlik Sense Engine Connection Errors
Session Timeout: The session has been idle for over 20 minutes in Qlik Cloud or the configured time in Enterprise, requiring a simple refresh.
WebSocket Issues: WebSocket (WSS) traffic is blocked between the browser and server, or network devices do not support persistent WebSocket connections.
Stopped Services: The Qlik Sense Engine Service (QES) or Proxy Service (QPS) is not running on the server.
Network/Proxy Interference: A firewall or proxy server is terminating the connection before the 30-second keep-alive packets can work.
Incorrect Host White Listing: The Virtual Proxy is not configured with the correct WebSocket host whitelist, especially when using custom DNS or load balancers.
Security Certificate Issues: Expired, invalid, or misconfigured SSL/TLS certificates on the Qlik Sense server.
Resource Exhaustion: Too many concurrent connections, exceeding the postgresql.conf maximum, or high memory usage on the server.
Troubleshooting Steps
Restart Services: Verify in QMC that Engines are running and restart the Engine/Dispatcher services.
This is occurring every day. Could you please let me know the solution for this? Is this happening due to heavy calculations in the app, or is it related to on premise RAM or a hardware performance issue?
