Are you getting a specific error message?

Firefox 48.0 is more than two and half years old. Is there a reason why you haven't updated to the latest version of Firefox?

Wesley Branton said

Is there a reason why you haven't updated to the latest version of Firefox?

Firefox 49.0 and later requires Mac OSX 10.9+ https://www.mozilla.org/firefox/49.0/system-requirements/

Actually the latest Firefox with security fixes for 10.6, 10.7, 10.8 was Firefox 45.9.0esr

Firefox 49.0 and later requires Mac OSX 10.9+

Thanks for the information James!

After looking into the issue further (with some further information provided by the original poster), this appears to only be an issue that occurs on older versions of Firefox.

They are receiving an SSL_ERROR_NO_CYPHER_OVERLAP error message. Upon further research, setting the security.tls.unrestricted_rc4_fallback option does not fix the issue, neither does anything else recommended for this error message.

If anyone else has any information on resolving this issue or a potential workaround, please let the original poster know.

At the moment, it appears that the issue can only be fixed with a computer upgrade.

Here's a similar thread from last week, possibly the same bank?

Would like to get to this web site https://www.vermontfederal.org/home/home always did, not now, message SSL_ERROR_NO_CYPHER_OVERLAP