Resolving Error Code 0x800F081F: .NET Framework 3.5 Installation Failure During Office 2021 Setup

Several approaches can resolve error code 0x800F081F encountered during Office 2021 installation. Below are the most successful methods:

1. Method 1: Manually Install .NET Framework 3.5
• Press the Windows key + R to open the Run dialog.
• Type 'appwiz.cpl' and press Enter to open the Programs and Features window.
• Click 'Turn Windows features on or off' on the left side of the window.
• Tick 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 Command Prompt as an administrator.
• Enter the following command and press Enter: DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:X:\sources\sxs(Note: Replace 'X' with the letter of your Windows installation media drive.)
• Wait for the process to complete and restart your computer.
3. Method 3: Use Windows Update Troubleshooter
• Open the Settings app and navigate to Update & Security.
• Click Troubleshoot on the left side of the window.
• Click Windows Update and then Run the troubleshooter.
• Follow the on-screen instructions to complete the troubleshooting process.
4. Method 4: Temporarily Disable Antivirus Software
• Open your antivirus software and disable it temporarily.
• Attempt to install Office 2021 again.
• Re-enable your antivirus software once the installation is complete.
5. Method 5: Perform a Clean Boot
• Press the Windows key + R to open the Run dialog.
• Type 'msconfig' and press Enter to open the System Configuration window.
• Click the Services tab and tick 'Hide all Microsoft services.'
• Click Disable all and then click OK.
• Restart your computer and attempt to install Office 2021 again.
• After installation, return to the System Configuration window and click Enable all.
• Restart your computer again.