If the letter did not come back to you, he received it. That part you can count on.
What happens after that is harder to read from the outside, and the silence does not necessarily mean what you are afraid it means. There are a dozen reasons an inmate might not respond right away. He may be working through complicated feelings about hearing from you. He may be in a stretch where writing feels harder than it should. He may be dealing with something inside that has nothing to do with you. He may simply not know what to say yet.
Here is something worth knowing from direct experience. Every piece of mail that arrives matters to an inmate, even when they do not respond to it immediately. Junk mail gets read. Catalogs get passed around. A personal letter from someone who took the time to sit down and write, who thought about this specific person enough to actually send something, that does not get ignored. It lands. Even if he has not written back, he has almost certainly read that letter more than once.
The question of whether he wants you to write again is best answered by writing again. Not a letter that asks why he has not responded, but a warm, uncomplicated letter that simply shows up the way the first one did. Consistency over time is what builds the kind of connection that eventually opens a door, whether that door is a response letter, a phone call, or just the knowledge that someone out there is still thinking about him.
Keep writing. See what happens. The worst outcome is that someone inside feels less alone for a few minutes, and that is not a bad outcome at all.