if (ContextCompat.checkSelfPermission(RegisterActivity.this, Manifest.permission.READ_PHONE_STATE) == PackageManager.PERMISSION_DENIED){
ActivityCom
Replace:
ActivityCompat.requestPermissions(this, new String[]{"Manifest.permission.READ_PHONE_STATE"}, 225);
with:
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_PHONE_STATE}, 225);
The actual string for that permission is not "Manifest.permission.READ_PHONE_STATE". Use the symbol Manifest.permission.READ_PHONE_STATE.