You might see Office error code 771 if your antivirus software, firewall, or proxy settings prevent you from installing Office. To resolve the problem, temporarily turn off your antivirus software, firewall, or proxy settings, install Office, and then turn the settings back on.
Causes for the Office install error
1. Your security software or your firewall might be blocking the Office installation.
2. Proxy settings are enabled on your computer.
3. Pre-existing version of an Office Suite.
4. Incomplete\partial\failed repair\installation\change\removal of the Office Suite.
Fixing 771 Office error code
Turn OFF Security software and Firewall:
First, temporarily turn off the antivirus and firewall security.
Then, install the Office 2013 or Office 365 Suite.
Follow the below solution steps to fix Office error code 771 while installing or uninstallig Office suite
1. Login to http://office.com/myaccount only if you have purchase Office through Microsoft Store.
If you purchased Office product key alone, go to http://office.com/setup and enter the product key.
2. If you have online account enter the username and password.
3. Click on the Install button
Click on downloaded file and installation prepares.
Office installation will start after checking and preparing the configuration.
Follow the simple onscreen instructions.
Once installation is completed, click on All Done button.
Now, the Office Suite is installed and ready for use and the error is fixed
You may check if the Microsoft Office applications are working fine.
If the issue is still not fixed, it can be a very critical problem with your computer. It can affect your personal data and the Windows Operating System. Windows registry and System files affected. It needs a manual removal and recommended to be performed by an expert.