Quickbooks is being run by client computer

I have an office where two computers run Quickbooks.  1 is the host, the other is the client or guest.  When the server is up and logged in the client can log in as a multiuser computer. But if the host computer is down and the client changes to a single user, this is where the issue begins.  The client cannot go back to being a Multi-user until the client (guest) computer is logged out of Quickbooks and then the host logs in first as multi-user.  How can I get the client to change over from single to multi-user if the host computer is not logged into Quickbooks?  When the host is not logged into QB and the client computer is logged onto as single user, when I go to file -  switch to multi user mode, it doesn't.  Again the only way it will switch is to log off QB on client and open QB on host first then open QB on client.  How can I make it so the client will switch back and forth from single to multi-user without having to log out?