I bottled NB American Amber Ale on April 11. The beer was then bottled with the priming suger on April 30. June 1st I tried the beer and it was flat. The beer had good flavor but no carbonation at all. I called NB and they said to repitch the yeast so I did on June 2. Today I cracked open one and no change the beer is still extremely flat. Any ideas on why this is happening? The beer is sitting in a closet and the temp is mid to low 70.