Please follow these steps to download, install and activate Visio 2021 Professional successfully on your computer:
1. Download the image file from Microsoft's CDN Server:
Click here to Download Microsoft Visio 2021 Professional 
2. Please click on the download link to download the image file. After successful download please double click the file and a new drive will appear under "This PC". Please access that drive to start the installation. The process is called image mounting. It is like if you would have inserted the DVD.
3. Install the software
4. Enter the product key provided by us and activate the software