Problem contacting Firefox from Emacs daemon started as systemd service

[Sébastien Gendre]

Hello.

I start an Emacs daemon at the start of my session with a systemd (user)
service. When I try to open an URL from Emacs, I got this error message
from Firefox:

Firefox is already running, but is not responding. The old Firefox
process must be closed to open a new window.

But if I call this command from a simple terminal:
firefox https://fsf.org

In Firefox, a new tab open on the FSF website, with no problem.

`browse-url-browser-function` value is `browse-url-default-browser`. That
mean Emacs call xdg-open, who call firefox command.


Have you an idea about this problem ? I can't found anything on the web.