I reported this in game but I want to post it here to see if anyone else has noticed this.
Last night I created 8 green, level 80 accessories (mostly rings but also a necklace or two). I put them into the mystic forge and they didn’t seem to combine at all. It took the 8 green items and returned nothing.
I then tried some level 70-75 green accessories and those went into the mystic forge just fine.
Has anyone else had this issue? Did I just get unlucky?