ThunderbirdPortable.exe not recognized as default Email client.

Greets. As always, thanks for the awesome work you do here.

I have the Thunderbird Portable 32bit version. Ever since the most recent update of Thunderbird (78.2.2) I can no longer get Windows to see it as the default for opening mailto links. It defaults to:

\PortableApps\ThunderbirdPortable\App\Thunderbird64 and in so doing asks me to create a new account.

I have tried editing the registry but it does not work.
I have tried to do the obvious by using the option to make Thunderbird default but it does not select \PortableApps\ThunderbirdPortable\ThunderbirdPortable.exe

The result is anytime I try to open a clickable Email address the 64 version asks me to setup a new account.