No colour change on Linux Mint

[LivingPharaoh]

Hi folks,
f.lux installed fine. It worked for a few days and maybe a week passed before I realised I was staring directly into the sun every night. It has stopped changing the screen. Clicking "Preview" in fluxgui does nothing. The button greys out for a few seconds as if it's momentarily previewing the setting.

How can I go about troubleshooting this?

Thanks

[gonsa]

I'm on Linux Mint too and yesterday I installed F.Lux without issues. The thing is it doesn't work. Preview doesn't do anything either.

Any suggestions?

Thank you