Similar to this? I had it redone with no issues to defroster... but there are still a few... I guess it could be one of a few reasons:
-was your car tinted before?
-they didn't clean the glass well enough (most tint shops do not operate in a 'air-tight vacuam' so contaminants get in some how or rather such as dust, etc)
I've also removed tint before just by using a handheld steamer...the steam heated up the left over residue which could be rubbed off easily with a micro fibre towel or even your thumbs.