Email hello@undersky.app. Common questions first:
Open Settings inside Undersky and tap "Restore purchases" on any device signed into the same Apple Account.
The rising sign depends on your exact birth time and place. A difference of even twenty minutes can change it. Check the birth time first; if you used "I don't know my birth time," the app uses noon and says so, which makes the rising sign approximate by design. Your Sun, Moon, and planets stay accurate either way.
Personalized readings require a recent iPhone. On older devices, Undersky still computes and shows your full chart; it just will not write the prose for it. Either way, your information stays on your phone.
Settings, then "Start over," erases everything: charts, people, and everything the app has tailored to you. Deleting the app does the same. Your information was only ever on your phone, so that is all it takes.
Undersky's data moves with a standard iPhone-to-iPhone migration or an iCloud device backup, because it lives in the app's local storage like your photos do. There is no Undersky account to sign into.
We take the math personally; the engine is tested against independent astronomy. Email hello@undersky.app with your device model and a screenshot, and if it involves a chart, the birth date you used.