Error when opening an external link : "Firefox is already running, but is not responding ..."

I used this program to make my FirefoxPortable2ndProfile as my default browser : https://www.winhelponline.com/blog/register-firefox-portable-with-defaul...

But now when I open an an external link from another program I always see "Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window."

I don't start with -no-remote and don't have MOZ_NO_REMOTE in Environment Variables either.

What am I missing ?