Firefox version 78 problem

Hi all - being fairly new to this Forum, I'm hoping you more experienced users will be able to help & advise me.

I had Firefox Portable ver 78 working just fine, on my 64 bit PC. When I run the Firefox78.exe from the installed folder it opens in 64 bit perfectly. But if I click on a link in an email (after checking it's safe!) or in a file of saved website links, Firefox opens in 32 bit minus all my add-ons. I don't want to run 32 bit, only the 64 bit version, but how can I force Firefox to always open in 64 when I click on hyperlinks?

I've followed various tips & tricks on the 'Net, but nothing seems to stop it happening. I'd welcome any advice on any more settings that I can change.

Many thanks if you can offer advice, Niloc81