Hi Sebastian,
Please note the following and check at your end.... (Even I struggled with this for a long time before finding the solution)
For BP Monitoring & Alerting -
You define the Monitoring objects under the Business scenario -- Business process
For BP Analytics -
You define the Monitoring objects under the Logical System.
Once you have defined, generated and activated. The data is collected for Analytics and can be displayed in the BPA area, usually after a couple of hours....
You may have done this already but I thought you might want to check it.
Regards
Deepak