I would check the failover status window from System Center --> Agents --> Failover and then continue the investigation. Usually, the log file SLFailover.txt (in C:\Skyline DataMiner folder) contains all the info related to failovers such as when a failover occurred etc. There is another file called FailoverStatus.txt in the same folder that shows the current state of the DMA in failover (whether it is going online/offline etc).