3 year old Hen with Impacted crop

[Traphill]

I have a 3 yr old Black copper Hen that started out with what I thought was sour crop, large mushy crop that would not go down by morning, this went on for several days she did not seem bothered at all. I isolated her gave her yogurt, grit and vinegar water. This has not helped and now it seems that she has impacted crop which now is not mushy but hard Chicken acts fine which I am very surprised! I have successfully treated impacted crop in the past and that chicken was not feeling so perky like my Stella is now.....Not sure what to do at this point....Any thoughts?
Thank you