If your guest ever tries logging in on the app and gets an error of "Can't Connect To Server" this can be caused by two things:
1. Internet Connection
2. Guest originally signed up using Facebook but isn't currently signed into FB on their device.
Things to check:
1. Confirm internet connection is solid.
2. Go to customer's timeline and scroll to the first post on their timeline. Confirm how they signed up.
3. If FB, have customer confirm they're logged into FB on the device currently.
4. If they log in and it still doesn't work, please submit a ticket to Punchh Support.