In order to use your Lyric Thermostat with Siri or Apple HomeKit apps, you will need to have a second generation Lyric Round Wi-Fi Thermostat and use a C wire.
In your Apple mobile device, navigate to your device Settings. Scroll down to locate your iCloud and tap to open. Ensure the following iCloud settings:
1. Actively signed in to iCloud.
2. iCloud Drive is turned On.
If iCloud Drive does not appear, or if you are still experiencing issues, turn off iCloud Keychain, then turn it back on. You will need to know your iCloud password and phone code. For more information, visit Apple's FAQ page https://support.apple.com/en-us/HT204085
3. Keychain is turned On.
You will also need to verify your Lyric app permissions are set to allow Home Data. In your Apple mobile device, navigate to the bottom to find your Lyric app and tap to open. Turn Home Date to On.