Outlook error 0x800C8101 typically occurs when the email client struggles to download or authenticate update files, often due to corrupted cache, misconfigured services, or interference from security tools—preventing you from updating Outlook or sending/receiving emails. To resolve it, restart your PC to clear temporary blocks. Then run the Microsoft Office Repair tool via Settings → Apps → Microsoft Office → Modify → Quick Repair (follow with Online Repair if needed) to restore Outlook’s core files.
Next, clear the update/download cache: stop the Microsoft Office Click-to-Run service, delete the contents of
%localappdata%MicrosoftOffice16.0OfficeFileCache, then restart the service. After that, open an elevated Command Prompt and run:sfc /scannow
DISM /Online /Cleanup-Image /RestoreHealth
This repairs system-level issues affecting Outlook. Additionally, temporarily disable any VPN, firewall, or antivirus software that could block update connections. Finally, reboot your system and relaunch Outlook—updates should now install, and the error will be resolved. For a complete step-by-step walkthrough with screenshots and troubleshooting tips, check out this guide.