Work through these checks in order
This separates an app-specific issue from a device-wide camera issue.
Confirm the app has camera access and that privacy restrictions are not blocking it.
A restart can release a camera service held by another app.
Some camera apps cannot save photos or video when storage is full.
Impact, liquid, focus vibration or a permanently black preview can indicate hardware trouble.
Before an erase, restore or repair decision
Confirm what data is backed up, what a reset or restore will remove, and whether you still need access to account credentials or authentication methods stored on the device.
When professional service makes sense
Hardware damage, repeated power failure, liquid exposure, battery swelling, damaged ports, broken displays and problems that persist after low-risk software checks can require qualified inspection.