Water not rising to icemaker?

I'm connecting a previously functioning icemaker that was without a water line for the last few years, but the fridge was still in use. The external line goes into the base of the fridge. A second line comes out of the base and goes up to the icemaker. I can see the water has risen about 2/3 of the way up the 2nd line to the icemaker, but has stopped. The icemaker is set "on" via arm position in the freezer. The external line is on. Not sure what is next. More info as I uncover it.