I have noticed that flow fails to connect every time I scan the QR code or manually enter the code on a rooted device with a custom rom. However it seems to work fine on non-rooted phones.
If this is because the phone is rooted I request the developers to enable this feature for rooted phones as well. I don't see any security or privacy threat using this feature on a rooted device.
Device- Oneplus 2
Rom- Resurrection Remix
Android version- 8.1.0 Android
PC software & mobile app are the latest version as of today.