Firstly, ensure that the Bluetooth is turned on within the IKAWA Home App Settings. This can sometimes toggle off when the app is closed or your turn off your device.  You can find this by heading to Settings on your iOS device and scrolling to IKAWA Home within the Settings folder and ensuring that Bluetooth is turned on.

When troubleshooting we have found that the tips within this article 

If your iOS device's Bluetooth functionality isn't working, there are several things you can try to get it working again.

Why Is My iPad/iPhone Not Finding My IKAWA Home?

Several things can prevent your iOS device from finding your IKAWA Home roaster, including:

• Bluetooth may be turned off on your iOS device.
• There may be other Bluetooth devices that your iOS device is connected to that are interrupting the connection. 
• Your Bluetooth device may be too far away from your iOS device.
• The device you're trying to connect to may not be sufficiently charged.
• Software could be out of date on your iOS device.

How Do I Fix the Bluetooth On My iPad/iPhone?

If you're having issues with your Bluetooth on your device in general, the steps below might help. Try each one until you find a solution that gets your Bluetooth working again. They're arranged from easiest or most likely to work to hardest or least likely to work.

1. Check to be sure your iPad's Bluetooth is turned on. It's easy enough to accidentally (or even on purpose) turn the Bluetooth on your iPad off. Check to be sure it's turned on, and then try connecting to your Bluetooth device again,

2. Make sure your devices are compatible. It seems like a given but believe it or not, not all devices are compatible. Make sure the Bluetooth device you're using with your iOS device is compatible. IKAWA Home requires iOS13.0 or later.

3. Make sure your devices are close enough. A Bluetooth signal tends to have a very short range, so make sure your devices are close enough to connect. Usually, 2-3 feet is good during the connection process, though you can often separate them by a greater distance once the connection is complete.

4. Make sure your iOS device is well charged. You wouldn't think the charge level on an iOS device you are using to connect to your IKAWA Home would matter, but it can. The more charged the devices are, the better the connection, so if you're having trouble and your device is less than 50 per cent charged, try charging your device and starting again.

5. Make sure your IKAWA Home isn't paired with something else. While it's true some Bluetooth items will connect with more than one device, that's not true for all of them. If you already have your IKAWA Home connected to something else, disconnect it and then re-try connecting it to the iOS device that you are using.

6. Turn Bluetooth off on your device and then restart your iOS device. If there's something 'wonky' in the works, a restart will often clear out whatever problem there might be.

7. Restart the IKAWA Home. After you've restarted your iOS device, the next step would be to restart your IKAWA Home roaster. Use the manufacturer's instructions for restarting the device, then make sure it's back in pairing mode and try to make the connection again. Just as a restart can help an iOS device, it can also help the IKAWA Home roasting machine that you are trying to connect.

8. Unpair and then re-pair your device. If you've previously connected your IKAWA Home to your iOS device, there could be some corruption with the connection. Try forgetting the device. To do that, open the Bluetooth settings on the iOS device, tap the (i) next to the device you want to forget, and tap Forget This Device. Once you do, restart the iOS device, and then try to connect the Bluetooth device again. The fresh connection may solve whatever issue is happening.

9. Make sure your iOS device is fully updated. Make sure it's updated to the latest version of iOS. 

10. Resetting your network settings is a little bit of a drastic step, as it will reset all your network settings, which means all your Bluetooth pairing and all your Wi-Fi networks will be removed. Your mobile network settings may also be reset (Which is only a problem if you're on a carrier that uses mobile virtual network operations such as Cricket, Republic Wireless, and other no-contract carriers in the US. If that is the case, you'll need to ask your carrier to help you reset your network settings).

    Once you reset the network settings, however, you may be able to connect to your IKAWA Home after you've reconnection to your mobile and Wi-Fi networks. Go to Settings > General > Reset and tap Reset Network Settings to reset network settings.

    For iPadOS 15 go to Settings > General > Transfer or Reset iPad > Reset > Reset Network Settings.

11. As a last resort, you can factory reset your iOS device. It's unlikely this will make much of a difference for your Bluetooth connections, but there's a slim possibility that something has been corrupted in your Bluetooth capabilities, so if nothing else is working, a complete reset of your iOS is worth a try, as a very last resort.

    However, be aware that if you reset your iOS device, you will lose everything on it (photos, contacts, etc.) so you might want to create a complete backup before you start if you need to do a factory reset.

Source https://www.lifewire.com/fix-bluetooth-not-working-on-ipad-5190776