Training readiness only updates from wake up in the morning and not the rest of the day on the app

1429345 said:

Training readiness on the app only updates when you wake up in the morning

Yes, that's the designed behavior.

From My Training Readiness Card Is Not Displaying in the Garmin Connect App | Garmin Customer Support: 

The intention of the training readiness report under Performance Stats is to be able to see your training readiness score from each morning when you wake up. This allows you to identify any possible trends that lead to various scores.

It was working correctly until a few days ago. How are you supposed to know how much you have recovered during the day in this case?

Personally, I always saw it working only in this way on the app. Real-time readiness is available directly on the watch.