If you have successfully paired your Tecla Shield to an iPhone, iPad or iPod Touch (it appears as connected in Settings> Bluetooth), assign your switches to Switch Control actions and turned on Switch Control and nothing happens when you press the switch, there might be an issue with the Switch Control settings.
There is setting called Hold Time, when this is on, you may need to press your switch for a set period before the action is performed. This function is incompatibly with earlier version of the Tecla Shield. Make sure this setting is set to off.
Also, make sure that Switch control is off or is restarted when adding switches or making configuration changes. Configuration changes will only take place after restarting switch control.