If you get an error code like the one shown below, there is an issue with your computer’s certificate authority settings. The Epic Games Store uses certificates issued by letsencrypt.org which relies on the ISRG Root X1 certificate to function. If your computer does not properly trust this root certificate you will encounter security errors like the one you are seeing.
Please try the following:
First, try to follow the steps in the article How to troubleshoot connection issues
Verify that your computer’s clock is set correctly. You can check your clock by going to https://time.is/. If it’s off by more than a few seconds, we highly recommend letting windows automatically synchronize your clock in the time and date settings.
Apply all Windows updates
To check for updates, select Start > Settings > Windows Update , then select Check for updates. If updates are available, you can choose to install them.
Ensure that the “Turn off Automatic Root Certificates Update” group policy is not enabled, or forced on by an administrator
- Press Windows+R, type regedit, and click OK.
- Navigate to HKLM\SOFTWARE\Policies\Microsoft\SystemCertificates\AuthRoot\DisableRootAutoUpdate.
- Change the value from 1 to 0.
- Exit the registry editor.
Reach out to a computer repair business to fix your OS installation
More info can be found here: https://letsencrypt.org/docs/dst-root-ca-x3-expiration-september-2021/