Reason # 1
There could be a possibility that customer has entered a version name value into the App Version Code field – e.g. 2.3. This field needs to be a whole number. We can suggest end-user to change the decimal value to a whole number such as 3 and then resubmit the build.
Reason # 2
This is a known identified defect with App Studio Portal whereby the keystore files must have a file extension while submitting the build form. However; we renamed the keystore file from USTSafetyKey to USTSafetyKey.keystore, uploaded it again & resubmitted the build.