Hello! The reason for the absence of "coffee grounds", as you call them, could be due to a couple of different factors. First and foremost, it's important to understand what, exactly, those coffee grounds are. Essentially, the laser is targeting dark spots/imperfections deep in the epidermis (surface of the skin), causing them to 'burn' and rise to the surface of the skin before flaking off.
1) Laser Intensity: If the laser wasn't set high enough to produce results, you will notice an absence of dark spots. This might mean that the laser didn't adequately reach the imperfections and thus eliminate them, causing them to rise to the surface.
2) Absence of Unnatural-Imperfections: IPL will work wonders on spots that have been caused due to sun exposure, scarring, etc. That being said, if an imperfection is naturally occurring within the skin of the individual (think natural freckles, etc.), such marks occur deep within the epidermis and dermis rather than residing only on the surface of the skin. Your skin does not look to have a large amount of imperfections and therein you might not experience much shedding. That being said - you might still experience the tightening of skin that IPL can produce.
As a general recommendation, follow up with your doctor to consider options for moving forward and address any concerns you might have.
In good health,