Do we know what might have caused the impaction?
Treats too early without grit, eating grass or brooder bedding, foreign object? Knowing 'what' is blocking things up may help with coming up with a plan to get it out or move things along.
How old? It'll be harder to treat the tinier they are due to how fragile chicks can be.
If it's full to the point of vomiting when you massage it, there's a risk if aspiration. Olive Oil is generally recommended to loosen things up, but it doesn't sound like you can provide it safely at this stage.
I've been lucky enough to dodge proper impaction so far and have only ever had slow emptying crops to deal with, so am only familiar with the basics on this one.
Is there any bad smell that may indicate rot or discoloration of the skin around the crop? Is it rock hard or squishy\fluid filled?
