The same issue happened for me and there was nothing in AppStoreConnect. Test Flight showed no details. I had to use the "Transporter" app (available in AppStore) to upload the app to App Store Connect. Then it showed the issues of the build I uploaded as shown below.

To get the build file to upload using Transporter, use the export option in the Distribute App workflow after creating the archive. You will end up with a ".ipa" file and that could be used to upload to App Store Connect through Transporter.