I had the same problem. It turned out that I for one had the volume turned on too low, I turned it up to twice the volume I currently had. And secondly, the most important part, was that I had to empty my mind, now whenever I want to enjoy ASMR I have to make sure that I don't think of anything while I listen. You can't think of anything except maybe the sound you're currently listening to, finish any thoughts/monologue that you might have before you start listening.
Now before I start listening I can lie in my bed for 15 minutes just thinking of things that could randomly pop up in my head and distract me while I'm trying to relax, and once that's done I can enjoy ASMR like I could when I first started listening.