Troubleshooting the 0x800F081F Error: Installing .NET Framework 3.5 for Office 2021

If you encounter the error code 0x800F081F while installing Office 2021, here's how to effectively address it:

1. Method 1: Manual Installation of .NET Framework 3.5
• Hit the Windows key + R to bring up the Run window.
• Enter 'appwiz.cpl' and hit Enter to launch the Programs and Features panel.
• Select 'Turn Windows features on or off' from the left side of the panel.
• Tick the box for '.NET Framework 3.5 (includes .NET 2.0 and 3.0)' and click OK.
• Complete the installation by following the prompts on your screen.
2. Method 2: Utilizing the DISM Tool
• Launch the Command Prompt with admin rights.
• Input 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 where your Windows installation media is located.)
• Allow the process to finish and then reboot your system.
3. Method 3: Employing the Windows Update Troubleshooter
• Access the Settings application and navigate to Update & Security.
• Select Troubleshoot from the left menu.
• Choose Windows Update and then select Run the troubleshooter.
• Follow the instructions displayed to resolve the issue.
4. Method 4: Temporarily Deactivate Antivirus Software
• Access your antivirus program and deactivate it temporarily.
• Attempt to install Office 2021 once more.
• Upon successful installation, reactivate your antivirus software.
5. Method 5: Conducting a Clean Boot
• Press the Windows key + R to open the Run dialog box again.
• Type 'msconfig' and press Enter to open the System Configuration interface.
• Click on the Services tab and tick 'Hide all Microsoft services.'
• Choose Disable all and click OK.
• Restart your PC and proceed with the Office 2021 installation.
• After installing, revert to the System Configuration and select Enable all.
• Restart your system once more.