Firefox portable won't start anymore.

Hi,
I have this problem.
Firefox portable won't start anymore.
I have tried different versions.
I have tried installing and uninstalling firefox, but it doesn't work.

It doesn't show up in the list of running apps, so I can't terminate it.

I tried manually cleaning the windows10 registry, deleted dozens of entries and it only worked once.
On the next attempt, it won't start again.

There must be something in the windows registry blocking it, but I don't know what.

Can you tell me how to fix it?

Thanks