This code, SSL_ERROR_RX_RECORD_TOO_LONG, doesn't come up that often but appears to be difficult to solve. Some of this may be repetitive, but just in case:

When you say you tried adding an exception, did you add an exception and it didn't make any difference, or did you not add an exception?

First, could you check your Firefox settings to make sure you are allowing modern protocols:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste TLS and pause while the list is filtered

(3) If you have any non-default settings (typically bolded and having a status of "user set"), you can make a note of the values in case they turn out to be important for some other reason, then right-click > Reset each prefer to its default value.

If you have any locked preferences (typically italicized), you may have an external lock file modifying your Firefox configuration.

Second, could you clear Firefox's Cache. See: How to clear the Firefox cache.

If you have a large hard drive, this might take a few minutes. If you do not see the number going down on the page, you can reload it using Ctrl+r to check progress.

Third, is there anything unusual about how you connect to the internet? You could check whether you have Firefox set to use a proxy server in settings, and switch that off as a test. You can do that on the Options page:

"3-bar" menu button (or Tools menu) > Options

In the left column, click Advanced. On the right side, click the "Network" mini-tab and then the "Settings" button.

The default of "Use system proxy settings" piggybacks on your Windows LAN connection settings, but you could try "No proxy" to see whether that helps.

An add-on still could override that, so...

Fourth, could you test in Firefox's Safe Mode? In 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 not running: Hold down the Shift key when starting Firefox.

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

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

Thank you for all of the detailed instructions! I tried every single thing on your list, and it still isn't working. Regarding your question on the exception, I tried to do it but it's possible that I didn't do it properly, so if there's something you would suggest I try around that, please let me know.

I just don't know enough about this particular error code to know whether it makes sense (or is possible) to make a site-specific exception.

To check whether you added an exception, you can view the Certificate Manager dialog.

"3-bar" menu button (or Tools menu) > Options

In the left column, click Advanced. On the right side, click the "Certificates" mini-tab and then the "View Certificates" button.

In this dialog, there are several categories of certificates. Exceptions are stored on the Servers tab. The ones with an "*" for the server name are built-in blocks for that issuer; you can ignore those and see whether you find any for specific sites.

Okay, I didn't see anything there related to Amazon.com. I clicked Add Exception, except that required me to type in the website address and click Get Certificate, and when I tried that it said it couldn't get a certificate so therefore I couldn't save it as an exception.

So still not sure... Hmm.

The less-typing way to add an exception is when you get the error page, look for an "Advanced" button and click that, then look for an "Add Exception" button. Firefox doesn't allow exceptions for all kinds of SSL errors, only some kinds.