There are a few things you can try when bluetooth fails. Give these a whirl and let us know if you're still stuck...
Things to check on your iPad (iOS)
Toggle Bluetooth off and on - Under Settings > Bluetooth - switch it off and leave for a few seconds. Then switch on and search.
Update iOS - Make sure you're on the latest update on iOS - Settings > General > Software Update
Force a restart - Switch off Bluetooth (Settings > Bluetooth) then power off the iPad. Turn Bluetooth back on.
Forget Device - Go To Settings > Bluetooth and locate your device. Press the (i) button on the right and tap on Forget this device then Confirm.
Full Network Reset - You can reset your network settings by going to Settings > General > Reset > Reset Network Settings. Please note: This will take a few minutes, reboot the iPad and reset all Wi-fi, bluetooth and cellular networks - which will need to be set up again. So keep your passwords handy and don't try this during service.
posBoss things to try
Make sure you are on the latest version of posBoss - head to the app store on the iPad and install any updates
Check your iPad is still compatible with the latest iOS and posBoss versions - more here.
Do a full Delete and Reinstall of posBoss to make sure you have the freshest of system files.
Other things to try
Restart your Bluetooth device.
Check for any Updates to your Bluetooth device's software or firmware
Contact or search the manufacturer's help docs for any known issues and resolutions.
Try a different iPad to see if the same issues persist. Another iPad on a different iOS version may work (there are a number of bluetooth issues reported on iOS 13)
Please do let us know what device isn't working, what model of iPad you have, what you've tried so far and what iOS you are running on.