Flash dashboard freeze on creating connection... how to trace?

Version: SAP Dashboard: 14.0.6.1036 – ver 4.0 SP6 Pach3

Help ...

When I start the cockpit from the server BO cockpit is loading and the final step "Making Connections" hangs. I use BEx queries in connection.

Nothing happens...

How do I find the cause?

Regards,
Grzegorz