If your Photoshop eraser tool is defaulted to erase to white all this time, but suddenly it is not working.
In short, your Photoshop eraser tool won't erase.
Don't panic.
Fix Photoshop Eraser Tool Not Erasing
This is what you do:
1. Close the image which you are working on.
2. Just leave it blank as shown below.
3. Now press on the these three keys on your keyboard:
Ctrl-Alt-Shift simultaneously (at the same time).
4. Now open your image back to Photoshop.
5. The eraser tool should be able to erase now.
6. That's all.