New alternator and new battery but still have to jump start

Had no issues with starting truck but the Battery light came on, had it tested and was told alternator was going out. I replaced alternator and now it won't start unless i jump it. Got new battery and same problem. Once I jump start it, it runs great. But when I turn it off will not start back until I jump it. What could be the issue? 2007 Grand Cherokee Jeep