Do a search here on BYC for "impacted crop, sour crop, olive oil, bread, and massage."
I have no experience with this, but have read many times on here how someone gave their chicken olive oil soaked into bread then gently massaged the crop (this can damage the muscles so be careful I have read) to move things through. I would not induce vomiting myself, although some have done it.
If it is truly impacted, there is a surgery thread for removing the impaction. If it is squishy then it might just be sour crop. Some chickens have this chronically I have read (pendulous crop)???
Just giving you some search terms to research this in case no one responds.