1. Please make sure that badge printing is enabled and configured correctly.
2. Ensure that you have the correct IP address of the badge printer QL-720NW QL-820NWB.
3. Ensure that firewall is configured correctly
InstaCheckin iPad app uses TCP port 9100 to communicate to the printer. Most corporate environments use some sort of firewall which would typically block this port. So, pleas make sure that the firewalls allow the communication from iPad to the badge printer over TCP port 9100.