Android 9 says : "Battery usage data isn't available"?

[LSMFTT]

This is what I see when I look for the list of battery usage by each app:
Settings > Battery > ┇ > Battery Usage > "Battery usage data isn't available".
Questions: Why? How to fix? Thanks!
Nokia 3.1 Android 9 (Android ONE version)

 

[B. Diddy]

How long has the phone been off the charger when you check this? If it's soon after fully charging, it may take a little while before it can start to figure out battery usage as you use the phone.