Well he's probably not that different than you are. If you were in his shoes and acted the way he did, you can probably think of reasons why he might act the way he does in the position he's in. i.e he's shy, he had a bad day, he's out of his comfort zone, he could be nervous/unsure of where he stands since it's early in the dating process etc. But you don't really know until you use what you observe to narrow things down. Just normal conversation can tell you a lot about someone.

You could experiment with different ways of socializing with him to see what gets him out of his shell. i.e if your dates have been around a lot of people, try picking somewhere quieter/somewhere away from larger groups.

It could be that he's not very comfortable making conversation when he's first starting to get to know someone new in which case, he'll probably be more comfortable talking the more you get to know him and vice versa. If he didn't have much issue texting you, it could just be easier for him to think of what to say because he doesn't feel pressure from the time constraints that talking to someone face to face has. If that's true, you're probably going to be the one initiating a lot of the conversation in the beginning until the ball gets rolling.

It could be that he didn't have a very good week or was otherwise stressed. If that's true then he's probably not going to vocalize that but it will likely be apparent in his body language and demeanor. In which case, be supportive but if he doesn't want to talk about it, that's fine, he will if he does.