I've known many guys who have been unable to climax from a blowjob. Not being the person who was receiving, I cannot comment on how good they were at the act.
In speaking with my mates, some people just don't enjoy having a woman's face down there, same as some women do not like a man's face down there. Personally, I like nothing more then a good blowjob, but everyone is different.
So I wouldn't be too worried, but remember there is always room for improvement
Read up on a few new techniques & hopefully you'll find what really floats his boat.
Oh, by any chance had he jerked off before your encounter? I know that from time to time, if I have jerked off a few hours before I make love that it can significantly increase the amount of time I last. In some cases I haven't been able to climax.