So I have the ESPN bundle, and I was able to watch the NBA Christmas games live without a problem. Now tonight, I am unable to do that. Does ESPN only livestream certain games for example on specific holidays? How can I watch normal NBA games live?
ESPN is one of the NBA's broadcast partners, but does not show nearly all NBA games. They (along with ABC) show 101 games this year, with TNT showing 65, NBA TV showing 107, and other games being only available on local channels in their local areas. There's a bit over 1200 total games in the regular season, for reference. Christmas Day is a special setup ESPN has where they show many games (that are all scheduled around their broadcast schedule); this is not typical for a normal NBA in-season day.
ESPN does not have streaming rights to NBA games, see this article for more details. You would need the NBA League Pass to watch (out of market) NBA games that aren't otherwise available.