I recently had the same problem with an older pen and I posted a question about it on other forums. Here is the solution as replied by JBWelda, who used to post here:
"Pump it up some by repeatedly pressing the tip down on a piece of paper. Should start flowing again. I have had this situation a time or two and was able to revive mine. If that doesn't start it up, dip the tip into a little puddle of 92 pct isopropol alcohol, and then pump it. I have had the same pens for over a year now and both work great still with the pumping exercise every once in a while. "
jb
All I can say is this procedure worked great. The pen chrome is good as new! Thanks JB!