There might be several reasons why the monitoring UI does not start.
You get error messages like 'Cannot retrieve language bundle' or 'Cannot retrieve severtiy rules'.
- Endpoints were not generated succesfully
The endpoinpts the monitoring UI is calling are created in SOLMAN_SETUP for EEM in step 2.4 (Configure Automatically)
When the WSDL has ben loaded succesfully but further WS calls are failing like in the screen shot then the following points could be the reason: 
- Missing authoriation.
The user does not have the correct role and authorization for this WS is missing. To verify this an authorization trace for the user in ST01 can be recorded when calling the monitoring UI. - Wrong WS configuration
During SOLMAN_SETUP you explicitly allow in
-> System Preparation -> Step 5.2 Web Service infrastructure Configuration
which authentication types all web services can use:
- Basic Authentication
- X.509 Certificate Authentication
- Ticket Authentication
If you don't allow for example Ticket Authentication it is not possible to logon first via SAPGUI to SAP Solution Manager and start from there in the workcenter the EEM Monitoring UI. The following screen shot shows the required settings when all authentication types should be used:
