Huawei p20 pro could not connect any Lights (except 650 celling) to yeelight app or mi home. I took my old Motorola g4 and connected everything. Can you check what is wrong with p20 pro and yeelight.
We will take a look. For now if you connected the lamp with your old phone, you can also get device list from P20 with the same account.
You will need to disable WIFI+ on your Phone. Then the connection works without too much of an issue. Huawei WIFI+ is interfering a lot with more than one device, since it allows to switch networks really quickly and takes control of Network Switching, which keeps nearly any smart home devices, from connecting at first.
I have configured several Yeelights, Amazon Echos and Google Homes using a P20 Pro and no device would be able to pair with the WIFI+ on. But you can always reenable it after completing the setup.
Thanks for sharing