Alternator Replacement

My battery started dying everytime I shut my truck off, battery was ok after being tested so tested alternator was not drawing enough power so put new one on, but still not getting any reading on dash, no electrical is working any ideas what issue could be?

I have a 2006 E-350 Van Conversion. It's been sitting for about 5 months and the battery I replaced just 5 months ago was completely dead when I went out to start it today. I tried to jump start it and when I first turned the key the dash indicator lights came on, but when I turned the switch to the crank position the dash lights immediately went out, and nothing getting to the starter. I rechecked the jumper cables for a good connection and tried to start it, but this time the dash indicator lights did NOT turn on, and it still won't crank. No dash lights, no dome lights, no head lights, nothing is getting power, even with jumper cables hooked up with the jumper vehicle running. Any suggestions specific to this van? What should I check that's preventing current to "everything?"