[Zubersoft]

It was listed in the original release notes for MobileSheets for Windows 10 (and it's also listed a few others places like the manual I believe), but you cannot connect the companion app to MobileSheets if they are running on the same machine. This is a limitation that Microsoft put in place for Universal Apps. They are not allowed to talk on the network to each other if they are running on the same machine. It's rare that you would need to use the companion app on the same machine as the Windows 10 version though, because it's far faster to just do the work in the Windows 10 version itself.

Mike