Signature is not being returned in transaction result object

[CC95]

I am using the Android In Person SDK and am trying to retrieve the signature from the transaction result object. Each time it is returning null. Here is my code where I am trying to retrieve it:

try {
   Log.i(TAG, "Sign base64: " + result.getSignatureBase64());
   
   byte[] decodedString = Base64.decode(result.getSignatureBase64().getBytes(), Base64.DEFAULT);
   //produces error because result.getSignatureBase64() is returning null
   Bitmap decodedByte = BitmapFactory.decodeByteArray(decodedString, 0, decodedString.length);

} catch (Exception e) {
   e.printStackTrace();
}

 Can someone please help me with this? My deadline is coming up soon and I'm lost on how to fix this.