OKay, let's try this in stages....
First do you have geoclue-2.0 installed? If not, then:
sudo apt-get install geoclue-2.0
If you get a message saying that it is already the latest version, then go back to the link I gave you earlier, get the sample configuration:
In terminal open pluma and the config file by typing:
pluma ~/.config/redshift.conf
Paste in the contents of the sample configuration. Find where it says:
[manual]
lat=48.1
lon=11.6
Then in a web browser search your location and latitude and longitude. Take the numbers which come up and plug them in the sample configuration open in Pluma. Once you've added the latitude and Longitude, save the file and close Pluma. Then try opening the application again. It should show up in the indicator section.