This has been happening the last couple of releases of Xamarin iOS. Visual Studio will lose the connection to the Build Host. Attempting to resync from Visual Studio gives me an error that there another instance of Visual Studio already synced to that Host. I am forced to Unpair and repair the Host and reenter a new PIN. This happens several times a day and is irritating enough in itself. What is worse though is that if I attempt to deploy in this state, Visual studio will attempt to build and then get stuck trying to deploy to the server. It never exits this state. Attempting to close the application gives an error that the application can not be shut down while a build is in progress. I am forced to kill the process using the task manager then restart visual studio.
This is a terrible experience and has been affecting productivity.