i have same problem , and i read about it
u have 3 troubleshootings
1-first one is light sensor , make light very dark and expose it to bright dark , if screen brught it so its normal
2- second one is dark sensor , when u have call ,cover the upper part by ur hand if screen turned to black so its normal
3-third one the front camera , if its on portrait mode not blurring the back ground so its not normal.
first one and second one its repairable face id
third one ( portrait selfie camera ) not repairable one