How to solve the error code 0x800F081F: .NET Framework 3.5 installation failure during Office 2021 installation

There are several ways to solve the error code 0x800F081F during Office 2021 installation. Here are some of the most effective methods:

1. Method 1: Install .NET Framework 3.5 manually
• Press the Windows key + R to open the Run dialog box.
• Type "appwiz.cpl" and press Enter to open the Programs and Features window.
• Click on "Turn Windows features on or off" on the left-hand side of the window.
• Check the box next to ".NET Framework 3.5 (includes .NET 2.0 and 3.0)" and click OK.
• Follow the on-screen instructions to install .NET Framework 3.5.
2. Method 2: Use the DISM tool
• Open the Command Prompt as an administrator.
• Type the following command and press Enter: DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:X:\sources\sxs (Note: Replace "X" with the drive letter of your Windows installation media.)
• Wait for the process to complete and restart your computer.
3. Method 3: Use the Windows Update Troubleshooter
• Open the Settings app and go to Update & Security.
• Click on Troubleshoot on the left-hand side of the window.
• Click on Windows Update and then click on Run the troubleshooter.
• Follow the on-screen instructions to complete the troubleshooting process.
4. Method 4: Disable antivirus software temporarily
• Open your antivirus software and disable it temporarily.
• Try installing Office 2021 again.
• Once the installation is complete, enable your antivirus software again.
5. Method 5: Perform a clean boot
• Press the Windows key + R to open the Run dialog box.
• Type "msconfig" and press Enter to open the System Configuration window.
• Click on the Services tab and check the box next to "Hide all Microsoft services."
• Click on Disable all and then click on OK.
• Restart your computer and try installing Office 2021 again.
• Once the installation is complete, go back to the System Configuration window and click on Enable all.
• Restart your computer again.