We are also impacted by this. This appears to be some kind of server-side regression because Apple is now rejecting assetFile / assetDescription pairs that previously uploaded successfully.
Using iTMSTransporter 4.0.0.4 on Linux an assetFile / assetDescription pair uploaded successfully on Sept. 25th.
As of Sept. 30th that same assetFile / assetDescription is now being rejected with:
[2025-10-01 21:43:07 UTC] <main> DEBUG: Setting System property: DataCenters = contentdelivery02.itunes.apple.com,contentdelivery01.itunes.apple.com
[2025-10-01 21:43:07 UTC] <main> DEBUG: Setting System property: DataCenters.host = contentdelivery02.itunes.apple.com
[2025-10-01 21:43:07 UTC] <main> DEBUG: Setting System property: DataCenters.setBy = Defaults.properties
[2025-10-01 21:43:08 UTC] <main> INFO: Configuring logging...
[2025-10-01 21:43:08 UTC] <main> INFO: Logging level set to eXtreme
[2025-10-01 21:43:10 UTC] <main> DEBUG: SMART-CLIENT: initializing data center locking ops: [authenticateForSession, validateAssets]
[2025-10-01 21:43:10 UTC] <main> DEBUG: SMART-CLIENT: initializing data centers with: [contentdelivery02.itunes.apple.com, contentdelivery01.itunes.apple.com]
[2025-10-01 21:43:11 UTC] <main> INFO: iTMSTransporter : iTunes Store Transporter [4.1.0]
[2025-10-01 21:43:11 UTC] <main> INFO: OS identifier: Linux <redacted>
[2025-10-01 21:43:11 UTC] <main> INFO: Memory: <redacted>
[2025-10-01 21:43:11 UTC] <main> DEBUG: SMART-CLIENT: getCurrent(); current data center is null
[2025-10-01 21:43:11 UTC] <main> DEBUG: SMART-CLIENT: getCurrent(); iterator was null, setting it
[2025-10-01 21:43:11 UTC] <main> DEBUG: SMART-CLIENT: getCurrent(); setting current data center to: contentdelivery02.itunes.apple.com
[2025-10-01 21:43:11 UTC] <main> ERROR: No value present
Package Summary:
1 package(s) were not uploaded because they had problems:
/<redacted>/<redacted>.pkg - Error Messages:
No value present
[2025-10-01 21:43:11 UTC] <main> DBG-X: Returning 1
This reproduces with both iTMSTransporter 4.0.0.4 and after upgrading to the latest 4.1.0.19 version.