Support
The app says a planet is below the horizon
That is correct behaviour. In Live and Grandeur, Umbra never lifts a body into the sky if its centre is genuinely below your horizon. Change the time, change your location, or switch to Beyond for an openly artistic placement.
The bearing looks wrong
Compass heading on a phone is an estimate and is affected by nearby metal and magnets. When Umbra cannot trust the heading it says “North not calibrated” rather than claiming alignment. Move away from metal and rotate the phone in a figure-of-eight to recalibrate.
The sky mask catches buildings or trees
The daylight mask is a heuristic, not a trained segmentation model. Pale buildings, cloud edges, thin branches and low light can defeat it. Use the manual sky boundary when the automatic mask is not behaving.
Looking at the Sun
Do not. Umbra provides no eye protection of any kind, and neither the app nor the eyewear concept should ever be used to view the Sun.