The experience can be different for everyone, but yesterday for example for myself when I went to go smoke DMT, I had the same thing you just mentioned. Mind you, the previous 3 times had been monumental breakthroughs. This one, everything was just completely dull and just not "connecting". Now, I don't know why this may be happening to you. For myself, I have a workable explanation. In my own case, when I'm holding my hits in, I'll start to get OEV holograms, and if I allow them to make their way over, and align just nice and properly with me, everything is vibrant and clear as a bell. If I don't do it, it's a coin toss, and if there's an obvious misalignment, I experience the dull, frustrating state I described above. I'm aware many don't experience DMT the way I do, but it seems like there are at least some who do, so I offer this bit of my experience in the hopes that maybe something resonates and clicks for you.
"Science without religion is lame. Religion without science is blind" - Albert Einstein
"The Mighty One appears, the horizon shines. Atum appears on the smell of his censing, the Sunshine- god has risen in the sky, the Mansion of the pyramidion is in joy and all its inmates are assembled, a voice calls out within the shrine, shouting reverberates around the Netherworld." - Egyptian Book of the Dead
"Man fears time, but time fears the Pyramids" - 9th century Arab proverb