Help when i build on android my sprites turn black

I've had the same problem as you. Only ONE sprite appeared all black. I searched for answers and found solutions regarding changing the compression to RGBA 16-bit or having the sprite dimensions in POT (Power of Two, 128 x 128, 256 x 256, 512 x 512 etc) as Mip Maps were enabled and only POT textures can be compressed that way, but it didn't make sense as other sprites were NPOT and they still appeared correctly on screen.

One of those might be the answer for you, but on my case, they weren't. I'm still not sure what was the problem, but what happened was that I ran the project on a tablet directly from Unity and it worked well. Then, I built the APK and uploaded it to Google Drive in order to download it later on other devices. The problem happened on 2 devices which download the APK from Drive. After my research, I was suspicious, and decided to download the same APK to the tablet where originally I had no issue with the sprite, and voila, the sprite was also black. So, I deleted the APK from Drive and reuploaded it again. It indeed worked fine on all devices I have tried before.

So, I'm not exactly sure what happened to the APK when it was uploaded, if it was corrupted somehow, but still installed and ran fine, but if, in your scenario, there's any upload/download of the APK involved, it might be worth a try to reupload it.