It's considered a blocked extra point and a return for a score. If your league scoring system did not have a rule in place for either the blocked extra point or an extra point returned for a score, then it would be zero points.
In the league I commish, the guy who had Denver's D threw a bit of a fit and demanded I award him 2 points. However we do not have a scoring provision for this play. I couldn't, and neither should any league, make a scoring change that is not in the league rules.