How to solve the error code 0x800f081f: Source files could not be found in Windows Server 2019

Error code 0x800f081f is a common error that occurs when trying to install or update a feature in Windows Server 2019. This error occurs when the source files required for the installation or update are missing or corrupted. Here are some steps to solve this error:

1. Check the internet connection: Ensure that the server has a stable internet connection. If the internet connection is unstable, it may cause the download of the required files to fail.
2. Use the DISM tool: The Deployment Image Servicing and Management (DISM) tool can be used to repair the Windows image and restore the missing or corrupted files. To use the DISM tool, follow these steps:
   a. Open the Command Prompt as an administrator.
   b. Type the following command and press Enter: DISM /Online /Cleanup-Image /RestoreHealth
   c. Wait for the process to complete. This may take some time, depending on the size of the image.
   
3. Use the System File Checker (SFC) tool: The SFC tool can be used to scan and repair corrupted system files. To use the SFC tool, follow these steps:
   a. Open the Command Prompt as an administrator.
   b. Type the following command and press Enter: sfc /scannow
   c. Wait for the process to complete. This may take some time, depending on the size of the system files.
   
4. Use the Windows Update Troubleshooter: The Windows Update Troubleshooter can be used to diagnose and fix issues with Windows updates. To use the Windows Update Troubleshooter, follow these steps:
   a. Go to Settings > Update & Security > Troubleshoot.
   b. Click on Windows Update and then click on Run the troubleshooter.
   c. Follow the on-screen instructions to complete the troubleshooting process.
   
5. Download the missing files manually: If none of the above steps work, you can try downloading the missing files manually from the Microsoft website and then install them on your server.

By following these steps, you should be able to solve the error code 0x800f081f and successfully install or update the required feature on your Windows Server 2019.