It sounds like the leap service isn't running. We ran into a similar situation. I'd check to see if the service was running, then I would load up Unity and check again. It was no longer running so I forced the leap service to start. If it's not working in builds for you, you may need to start it either manually or maybe create a batch script in the same folder as your exe that starts the service.
We did update to the latest 5.2 and we haven't run into this issue again. However, it's only been like 3 working days so I'm not too confident whatever was causing the service to stop running was fixed. Also, the name of the service changed between 5.1 and 5.2.