Try talking to grandma again and click the first option (turn in ingredients, even if you don't have the 11th one). The gradma will say you have helped her 10 times and give you the ring. At least that's how it worked for me. Of course, if your inventory was full during the time, then it seems to be an actual bug and needs to be fixed by GMs
Don't worry about it. We got you covered for this. Most likely nothing will be done until at least the next update.