Installation error: certificate or location is not trusted

When trying to install the Encyro Outlook Addin, I get an error that starts:  Customized functionality in this application will not work because the certificate used to sign the deployment manifest for Encyro Secure Files and Messages or its location is not trusted.

The issue is that for some reason your computer is not trusting the website https://apps.encyro.com. The fix is as follows:

• Open Internet Explorer (even if that is not your favorite browser). If you do not see the Internet Explorer icon, type "Internet Explorer" in the Windows search box near the Start button in the bottom left of the screen.
• Click the gear icon towards the top right and then click Internet Options.

• Click the Security tab and then click Trusted Sites. Next, click on the Sites button.

• In the dialog that opens, under "Add this website to the zone:" enter https://apps.encyro.com and click Add.

• Click Close and then on the previous dialog, click OK.
• Now try installing again by visiting https://apps.encyro.com/ and clicking Download. You need not use Internet Explorer but may use any browser (Chrome, Edge, FireFox etc.).