Any Exchange Admins worst nightmare is when you reboot your Exchange server and the Information Store Service won’t start.

There can be many factors why this can happen and the event logs will also give you details of why it failed, but in this scenario the failure was not what was expected.

When checking the DAG, we noticed that the copies were in a failed state and normally go healthy within a few minutes and start replaying logs but in this case it didn’t.

Upon investigation the Information Store Service was not started and starting it gave the following error:

Oh boy, so now we turn to the event logs to see why:

Not what was expected, we had a time sync issue. This will cause errors like this and others and found that the system clock was out by more than 5 minutes, correcting this by removing time synchronisation from the VM Guest services and starting the VM up again resulted in the Store service starting again and all back online.

Hope it helps.