hii Firefox_Bug_Report,

what does the error page say? Is it a Constant Contact error page or a Cloudflare error page?

Firefox users may be using Cloudflare for DNS lookups -- this is the service that associates a server's name with its numeric IP address. If you have problems with servers not being found, you can turn that off on the Options page. More info in this article: Firefox DNS-over-HTTPS.

When you first launch a private window, it does not have any data about the site, so it has a fresh cache and fresh cookies. So one possible thing to try -- in regular windows -- would be to clear Firefox's web cache and your cookies for the site:

(1) Clear Firefox's Cache

See: How to clear the Firefox cache (just the web cache, not all site data)

If you have a large hard drive, this might take a few minutes.

(2) Remove the site's cookies (save any pending work first). While viewing a page on the site, click the lock icon at the left end of the address bar. After a moment, a "Clear Cookies and Site Data" button should appear at the bottom. Go ahead and click that.

In the dialog that opens, you will see one or more matches to the current address so you can remove the site's cookies individually without affecting other sites.

Then try reloading the page. Does that help?

Testing in Firefox's Safe Mode: In its Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is running: You can restart Firefox in Safe Mode using either:

"3-bar" menu button > "?" Help > Restart with Add-ons Disabled (menu bar) Help menu > Restart with Add-ons Disabled and OK the restart. A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

If Firefox is not running: Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.) A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement? Thanks regards -Arman

Note that ESNI is deprecated and is replaced by ECH (Encrypted Client Hello).

• https://blog.mozilla.org/security/2021/01/07/encrypted-client-hello-the-future-of-esni-in-firefox/
• https://blog.cloudflare.com/encrypted-client-hello/

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