It was working after you took it apart. So I think the problem is with either the new solenoid. Or there's something going on with the starter. Possibly related to the recent disassembling. Probably not, since it was working.
So I'd check voltage again, then put the old solenoid back on it, for testing purposes. Check operation again, see if it made a difference.
But if everything else checks out, I'd take it apart again. Or replace it.