why cant i get past step 2a: `:express(error): Could not read private key`

here's the error:
```
Building aab for platform: android
Enter pass phrase for private key:
:express(error): Could not read private key in /c/Users/cf86c/OneDrive/Documents/GitHub/UrsinaForMobile/src/private.pem.
        Failed to sign /c/Users/cf86c/OneDrive/Documents/GitHub/UrsinaForMobile/src/dist/my ursina game-0.0.0_android.aab.
```