Green’s Dictionary of Slang

Aus. phr. denoting ‘I am not pleased;’ ‘you have upset me’.

2001		Whirlpool Broadband Multimedia 4 Sept. 🌐 Telstra ADSL customers ‘not happy... Jan!’ [...] Almost half of the Telstra ADSL customers surveyed in a magazine poll said they ‘often’ experienced technical problems with the highspeed service.
2003		Woroni (Canberra) 18 Aug. 8/4: The fact of the matter is that the Liberals would make more money available for the Commonwealth subsidisation of student places than Labor, yet the Libs get slammed and Labor gets a free pass for providing less money. NOT HAPPY JAN.
2007		P. Anderson Melbourne’s Gangland Killings 111: ‘Not happy, Jan.’ I can recall that the car windows were down and the bullets were going that close you could hear them singing past.
2012		‘Rubi Red’ Turn Left at the Ocean 111/4: It was not a pretty sight, and, ‘Not happy, Jan!’.