App Store Distribution rejected

I'm trying to submit an app that we have successfully tested in TestFlight.

After completing all the distribution steps and submitting for review, the review is failing with the response:

"Your app version was rejected and no other items submitted can be accepted or approved. You can make edits to your app version below."

I haven't received an details in app or via email to provide further information.

The version in TestFlight that I have uploaded is: v1.0.23(23). When entering the distribution details, and from the rejection response., it looks like the version number I'm entering on the main distribution page is the issue - maybe? I have tried entering 1.0.23, 1.0.23(23), even just 1.0 - but it constantly keeps getting rejected.

Is it really the version no. that is wrong, or potentially something else? How can I get more information on why the submission was rejected?