Maybe you have it switched off,
If I am right you are talking about the "cup of coffee" reminder that tells you it's time to rest a little,
If your car has it you should be able to acess its settings in the little screen.
Hope it helps.
I have had it once, on a short ten minute trip on a very narrow and twisty 'B' road, where I had to cross over the centre line several times. Up came the coffee cup! Can only presume 'it' thought I was starting to nod off so suggested I should take a break?