I have had the same problem since I switched to GNOME 3 in Debian "testing". This is the output from the console.
$ redshift Cannot list GNOME panel applets. Initialization of gnome-clock failed. Trying next provider... Latitude and longitude must be set.
$ gtk-redshift Cannot list GNOME panel applets. Initialization of gnome-clock failed. Trying next provider... Latitude and longitude must be set.
I have had the same problem since I switched to GNOME 3 in Debian "testing". This is the output from the console.
$ redshift
Cannot list GNOME panel applets.
Initialization of gnome-clock failed.
Trying next provider...
Latitude and longitude must be set.
$ gtk-redshift
Cannot list GNOME panel applets.
Initialization of gnome-clock failed.
Trying next provider...
Latitude and longitude must be set.