This can happen if that NAS devices only supports TLS 1,0 and 1.1 and doesn't meet the current requirement to support TLS 1.2 or 1.3. Isn't there an update available for the firmware of this device to support TLS 1.2 or newer ?

There is still a way to override this and re-enable support for those older TLS versions, but this is not recommended. If you want to proceed then you should only use this when you need to access this NAS device and not for visiting websites.

• about:config => security.tls.version.enable-deprecated = true

You should reset this pref after you are done with this device.

You can open the about:config page via the location/address bar. If you get the warning page, you can click the "Accept the Risk and Continue" button.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Holy cow, What a convoluted process. However, I found the setting and figured out how to change from "false" to "true"

FIREFOX !!!!!!!!!! HOW ABOUT A BUTTON FOR THIS!!!!

Thanks mucho

BTW NAS unit has its latest update ReadyNas Duo 4.1.16

FIREFOX !!!!!!!!!! HOW ABOUT A BUTTON FOR THIS!!!!

As said it is not recommended to do it for security reasons except temporarily. https://hacks.mozilla.org/2020/02/its-the-boot-for-tls-1-0-and-tls-1-1/