1. Has it ever worked? Did anything change since last time working?
2. Is QOS being written to the Database? (you can verify this by creating a Performance Report Designer graph with the qos you are using for the availability reports - Or within the same SLM portlet go to Quality of Service > Browse to the net_connect qos in question and check if the you see one target for each of the servers you are monitoring.
• If you see current QOS for all your targets, then you know that there might be something wrong with how you are creating, seeing or exporting the availability SLA report.
• If you Don't see the QOS for all your targets, then there might be a problem like: Database Server issues, Data_engine connection issues to the Database Server or stuck QOS hub to Hub Queues