This is most likely an issue with water in the mast or freezing temperatures

1) If it had recently rained and if water is seen coming out of the weep holes when raising the mast, then draining the water out should fix the problem. To do this, raise the mast as far as it will go, then lower the mast back down, and repeat until the mast makes it all the way up and no more water comes out of the weep holes on the mast.

2) If the issue is not water related, then freezing temperatures could affect the seals on the mast sections either causing the mast to get stuck or air escaping from the seals. If this is the case, the only solution is to let it sit out in the sun or use heating blankets to warm up the mast.