This is a common problem with iOS devices and is due to corruption of connection files, this sometimes happens after an update to iOS. It's an easy fix in most cases.
You just need to go to Settings> Bluetooth then the Tecla Shield will be listed under devices (most likely as connected), press the (i) next to it and select Forget device from the following screen.
Turn off Bluetooth on your iPad, turn Bluetooth back on after about 10 seconds and re-pair your Tecla Shield that should be listed there now as Not paired. That should enable re-connection.
If that doesn't work you may need to reset your settings, here are the instructions:
Reset your Network Settings. Tap Settings > General > Reset > Reset Network Settings. This also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you’ve used before.