Are they just on/off, or do they have settings?
Also how long were they on?
I know on my bikes with heated grips I always put them on high while warming up the bike.
Otherwise, my hands are cold before I feel the warmth from the grips so then they are playing catchup.
Once warmed up I can never set them higher than about a 1/3 of the heat range.
The grips I have owned range from OEM Kawasaki, Harley, Yamaha, Triumph, to Oxford on a few bikes.