Keep losing my premium version subscription with no resolution – Storm Radar: Weather Tracker Review

In recent months this app on my iPad is unstable. It disappears. I send notifications. Eventually it reappears.......lasts for a week or so......then disappears again. I have an annual premium subscription but the instability is not acceptable, no the resolution effort. I need the app; I am a weather spotter. I may give up. The app works fine on my iPhone. Very disappointing.
Review by LizFri on Storm Radar: Weather Tracker.