If an employee has clocked in from the mobile app(or has been clocked in by someone else via CrewClock), as long as the mobile device has a data connection you should be able to see the clock event immediately on the Who's Working Now Screen (located under your TimeSheets menu in the website). Occasionally a clock event may not be synced immediately, and in that case there may be some delay before the event is visible on the website.
A sync delay can occur for various reasons, but usually is caused by a poor data connection and or short delay in obtaining a GPS location. In that case, the mobile app will periodically retry sending the punch until it succeeds.
In no case will the clock event be lost, unless the employee logs all the way out of the mobile app while there are unsynced events on the device.
If you are not seeing an employee clocked in, first make sure you are on the Who's Working Now screen. You will not see a currently clocked in (open) employee time segment on the View Time Sheets screen. Once a segment of time is completed, it will be closed out and moved from the Who's Working Now Screen to the View Time Sheets screen. So if an Employee is working now, you'll see it on the Who's Working Now Screen, and once they finish a segment of time (i.e. Clock Out or Switch) then you will see the completed segment of time on the View Time Sheets Screen.