Same happened to me a lot. I was also worried, but some replied after some days saying that they got busy or was sick etc. And some officially didn’t get what technical terms I was talking about, not their fault, they wouldn’t have come to me if they knew everything. So, I started keeping it simple according to the buyers. Try to reply to them in their language in how they have knocked or explained their project works. Don’t get too simple on the experts though, they might think you don’t know anything. In one sentence, match the buyers profile while replying.
The key is to not getting depressed on it and don’t hold on to it. Keep sending offer requests and mostly improve your gigs anyway possible. A good gig and profile with work examples and portfolios are always eye-catching.