Same problem here. Battery+ stopped recording historical data and now only shows the current battery level.
It no longer shows time remaining, run time, charges, run time and max life charts, the record or percent charts.
The most irritating thing is the Battery+ Push Pins keeps popping up and taking me out of my current app and back to the watchface.
I haven’t tried a reinstall yet, but the watch has been rebooted several times. I also confirmed Battery+ is selected as a background app and have tried toggling it off/on.