No water coming from water supply line to icemaker
I'm assuming you have a connection like this:



I've seen these fitting leak, but I've never seen them have no flow before.

Generally these compression fittings don't need to be on very tight, because it's the pressure of the sleeve against the fitting that keeps them from leaking. Usually they only take about one half to one full turn with a wrench after being hand tightened.




Things to check:


Make sure the brass insert is not crushed or bent
Make sure the sleeve is on straight, has no nicks or other damage, and seats well in the fitting
Check the tube isn't folded over or crimped (if it is, cut it off a bit past the damaged part)
The end of the insert shouldn't sit too deep within the valve. Generally the sleeve should be about centered over the insert.
Check for blockage or dirt in the valve and on the edge of the fitting where the sleeve sits