This article will show you how to reduce your watch battery usage to last more days.
Still not solved? Reinstall Notify app to restore default settings (do not import any backup).
Alternative solution: reset only app settings (keep fitness data) by doing reset app settings from the app general settings on main left menu
If you watch has more than one year, disable your phone Bluetooth (or install only official app) to check if battery drain is related to Notify app or not