Understand Azure Traffic Manager (TM) failover mode

Hi,

I use the TM in Failover method.
An hour ago, we had some routing issues to our cloud service, but the TM didn't failover.

Querying the data, I can see that there was a deduction of TM "ping" transactions to my service, from ~16/min to ~10/min.

I could not find so far any documentation to understand the TM logic on failover mode.

Can you pls assist?

when it decides to failover?

thx,

Or