I primarily use Firefox 64. I have Firefox 32 on my computer to use when a website can't handle Firefox 64, e.g. San Diego Gas & Electric. Both versions are current, version 75.0. When I open Firefox 64 each day I get a diagnostic saying that it is not my default browser (Firefox 32 is). So, I've tried to change my default to Firefox 64 but nothing works - there are 3 "Firefox"s listed when I click on the default settings page and I've tried every option I can think of but I can't seem to change my default from Firefox 32, even going to IE, Edge, Chrome as default then back to Firefox 1, 2 or 3.

How do I make Firefox 64 my default? Should i try to uninstall Firefox 32 and then see if I can ger Firefox 64 as my default before re-installing Firefox 32?