The leave-on timer stopped when I locked my phone
It should not. The timer keeps running in the background and posts a notification at zero, so allow notifications in Settings, then SebDerm, then Notifications. If iOS Low Power Mode is on, delivery can be delayed by a minute or so.
The scanner says unknown for several ingredients
That is deliberate and it is the honest answer. The ruleset covers ingredients with a documented association with Malassezia growth. Anything outside it is marked unknown rather than safe, because calling an unrecognised ingredient safe would be a guess presented as a fact.
My weekly score went up but my skin feels the same
Tap the score to see every component that produced it. The number is built from the items you logged, and expanding it shows which one moved. If a component looks wrong, correct that day's log and the score recalculates.
Photos are not lining up week to week
Use the camera guide, which fades your previous photo over the viewfinder. Match the outline before you tap, and keep the same lighting and distance. Two photos from different angles will look like change that is not there.
I subscribed but Premium is still locked
Open the Premium screen and tap Restore Purchases, and make sure the device is signed in with the Apple Account that made the purchase.
Can I move my data to a new phone?
Not automatically, and this is the honest cost of the privacy design. The app has no server and iCloud sync is off, so there is nothing in the cloud to restore from. Export your PDF before you switch phones if you want to keep the record.
How do I delete everything?
Delete the app. Everything it holds, including all photographs, is stored inside the app on this device and goes with it. There is no server copy, because there was never a server.