Can't upgrade to Windows 11 Build 26340.9354

Because the upgrade rolls back even after a fresh installation, another round of SFC is unlikely to identify the failing setup phase. The code 0x8007042b alone does not name the responsible driver or component. Before another attempt, preserve the setup logs and open the automatically generated SetupDiagResults.xml under Windows, Logs, SetupDiag. Microsoft's SetupDiag guidance says the last reported failure is typically the fatal one when several failures appear. Record that rule, its error, and the setup phase or operation, rather than only the Windows Update message. Include the Panther and Rollback logs from the failed attempt, your current build, hardware model, and Insider channel in a Feedback Hub report. Remove personal information before sharing excerpts publicly. Do not use an unofficial image simply because a download generator failed. The evidence here does not establish a known build-specific fix or justify another clean installation.