I have the same issue, but I think the problem might be the router. If you have your Mac getting an IP dynamically, it may change on a boot/restart. I think, instead of using an IP to identify the WiFi Sync Server, the Enpass should use network name.
However, I am currently testing reserving the IP for my Mac and will see if that resolves the issue.
If that doesn't work, the sync process times out after a few minutes. If you're quick, you can disconnect the device from WiFi Sync and reconnect with the QR code