Windows Admin Center is a locally deployed, browser-based app for managing Windows servers, clusters, hyper-converged infrastructure, as well as Windows 10 PCs. It is a free product and is ready to use in production. When prompted with an error when trying to access WAC from other browsers saying the site is not secure. In this guide, I will show you how to fix Certificate Error: Unable to access Windows Admin Center from the Web. Please see How to upgrade Windows Admin Center, How to setup Windows Admin Center on a Windows Server, How to setup Windows Admin Center on a Windows Server, how to Transfer Data from Windows to MAC, and How to mount a USB Drive in Linux.

The root cause for not being able to access Windows Admin Center from the Web

A self-signed certificate option was selected during the first installation. See the following links for “How to setup Windows Admin Center, “How to install Chocolatey” and “How to install, upgrade and uninstall software with Chocolatey“. You may also be interested in Winglet, which is also a Windows Package manager “Winglet”. See how to install Winglet and how to install applications with Winglet CLI.

Solution

Uninstall WAC, and reinstall the WAC. On the WAC Installation page
– Select the second option and
– specify the thumbprint and click on install.

Alternatively, under Program and features, right-click on the WAC porgram and click on "change".
- Please follow the steps as directed. 

I will recommnd using this method!

And click on Install. This should fix the issue. Other Possible problems can be found in this link. Here is a great posts: How to install Windows Admin Center (WAC) in an unattended mode using a self-signed certificate. Also, see How to schedule and run update via Windows Admin Center.

I hope you found this blog post helpful on how to Fix Certificate Error: Unable to access Windows Admin Center from the Web. If you have any questions, please let me know in the comment session.