If the principals lose connection that is the state of the cause.If the connection is established the databases will revert to their normal states.Causes of that could be:
1.DNS server is down
2.Link between the principals is down
3.You change the user that is running sql services(to one that cannot run them)
4.SQL Server Agent is not running on either or both servers
“When I hear somebody sigh, ‘Life is hard,’ I am always tempted to ask, ‘Compared to what?’” - Sydney Harris