As others have noted, in order for our eyes to see the glow from tritium laps, typically, we need at least to have begun dark-adaptation: not "being dark adapted," in the canonical sense - rather, just that our eyes have adjusted to darkened surroundings.
I explain it as the reverse of heading outside from a movie theater.
It does stand to-reason that the more intense the glow, the easier/quicker it is for our eyes to pick up. However, for most typical tritium night sights, there just isn't sufficient brightness. "Larger" sights like the XS-Big Dot, particularly when newer, can make for an easier/faster transition, but even so, a lot of it depends on just how fast *_your_* eyes start to adapt from the transition.
To-wit, this is why sights like the Trijicon HD and others similar use a phosphorescent painted ring on the front post that highlights the tritium lamp. Much like the "lume" painted onto the hands/dials of some modern sportswatches, this not only allows for easy pick-up of the front post under daylight or otherwise brighter conditions, but with that painted ring being "glow in the dark," it allows for a much more intensely visible reference point on that front post as the shooter transitions from a brighter ambient to a darker ambient (e.g. stepping into a darkened warehouse after having drawn the gun while outside [thereby allowing that "glow in the dark" paint to "recharge"). While this "glow in the dark" ring fades quickly with time, the idea is that the shooter's eyes would be sufficiently acclimated to the dark by that point, allowing for the ability to pick up the dimmer tritium element.
As
@10mmLife noted, without seeing the sights in-person, I think it's hard for us to say whether your initial set was truly defective,
@ajz1966 , or if your expectations were possibly a little too high. From my search on XDTalk, there's only one thread with complaints of the front tritium lamp....but I do understand that's a single-point source that I'm referencing from.
That said, physical damage to the tritium lamp is definitely possible, as
@ddeuce22 noted, and many times this comes about as a result of installation issues. I, too, am disappointed that your replacement was sent out defective, but it is possible that there was only a very, very small leak at the time it was pressed-in and passed Q/C...only to arrive to you after the gas has fully dissipated. In your shoes, I would try to contact SA again and let them know of the fact that the replacement set arrived DOA, and see if they are willing to make-right with some kind of extra compensation for your time and frustration.