Well, it's almost 2am here in the UK and both @Andrew Nelless and @Dan Sorahan are asleep. Since the cloud server is currently experimental, they're the only ones who know how to maintain it. I'll get them to show me how it works tomorrow so I can fix it if this happens again.
I'm really sorry, but it looks like it'll be offline for the next 8 or 9 hours. Please email us if you need a refund: [email protected]
You can always downgrade temporarily to Synergy 1 in the meantime: https://symless.com/synergy/downloads