Note that Floranext now only supports Stripe BBPOS Credit Card Reader. The Miura is no longer supported for new customers.
Device not found error means the device is either turned off, sleeping, or is not paired to your iPad.
Press the Power button (blue button on top of device) once to wake the device, then wait 8 seconds and try again.
If the device does not wake when you press the power button, it likely has run out of battery life and needs to be charged. Plug in the power card to the top of the device to charge. You may continue to take payments even while device is charging.
If this does not solve the issue, check the device is paired to your iPad.