SSL_ERROR_BAD_CERT_DOMAIN

Assuming that you haven't figured this out yet, I do have experience with doing this in Firefox. So, here you go:

1. When an alert appears in your Firefox web page which says "Your connection is not secure", click or tap on the "Advanced" button that is located in the bottom right corner of the warning window.
2. On the next window that appears, Firefox will explain to you why you are being prevented from entering the site.
3. Click or tap on the "Add Exception" button that is located in the bottom right corner of the warning window.
4. On the new window which appears, Firefox will again offer you a warning, just to make sure that you really want to do what you are about to do. There will be a few options to view the contents of that site's certificate. On a side note, sometimes this security warning comes up because the site is using a self-signed certificate, instead of one that has been issued by an actual certificate authority. There is really no need for self-signed certificates anymore, because even if one cannot afford a commercial certificate, there are services such as LetsEncrypt which offer free, valid certificates which are even recognized by Google.
5. If you want this exception to be permanent, make sure you click the box that says "Permanently store this exception".
6. Click on the button in the lower right corner of the window that says "Confirm Security Exception".
7. You're done.

If you need to manually add a security exception to Firefox -- in other words, not when you are actually blocked from entering a site, but at any other time -- do the following:

1. Under the "Firefox" menu, select the "Preferences" option.
2. In the new window, click or tap on "Privacy & Security".
3. Scroll all the way down to near the bottom of the page to the "Certificates" section.
4. Click or tap on the "View Certificates" button.
5. Near the bottom of the "Certificates Manager" window, click on the "Add Exception" button.
6. On the new screen that pops down, enter the URL of the website you want to add an exception for.
7. Click or tap on the "Get Certificate" button. You can then click on the "View" button to see the contents of the certificate.
8. Enable the "Permanently store this exception" box if you so desire.
9. Click or tap on the "Confirm Security Exception" button.
10. You are done.

With Chrome, the process is simpler. Here are the instructions:

1. When an alert appears in your Chrome web page which says "Your connection is not private", click or tap on the "Advanced" button that is located in the bottom left corner of the warning window.
2. Next, click or tap on the "Proceed to example.com (unsafe)" button that is located in the bottom left corner of the warning window. Of course, it won't really say "example.com". It will have that actual domain name of the site you are being prevented from entering.
3. You are done.

Please let me know if the above is helpful to you, and/or if it resolves your issue. Thank you.