Authentication failures
If transmission never starts and access or credentials are rejected, check the team, app access and authentication method first. Confirm that credentials belong to the right account and have not been revoked. Ask an authorized person to supply replacements. Never post certificates, API private keys, passwords or complete authorization requests in public support threads.
Interrupted transfers
Record time, progress, file size, network and the original error. Verify that the file is fully readable; compare its size or hash with the build owner if copying may have failed. Check Apple Developer System Status. If testing another connection, use a trusted network rather than disabling HTTPS certificate verification.
Package-validation failures
For an explicit validation error, inspect the indicated Bundle ID, version, build number, signing or package setting. Give the full error to the build owner, fix it and generate a new package. Renaming the IPA or changing upload tools cannot repair its contents. Do not delete previous builds or recreate an app merely because an upload failed.
Processing after upload
Once the tool reports completion, investigate Apple’s processing stage. Check Build Uploads, build status and the developer mailbox before deciding to upload again. Share team, platform, Bundle ID, version, build number, time and a redacted error with support. Avoid promising a fixed waiting time or retrying the same upload indefinitely.