Don't wise people in the world always say, "patience is a virtue?" This is especially true in salary negotiation. You may be fully on board with the salary and compensation you believe you deserve, but it could still take significant work to convince others of this. You are very likely to get everything you want, simply because you asked. (That being said, not asking at all certainly will not get you what you want)!
Employers expect that 1) many potential hires won't even try to negotiate, and 2) that those who try to negotiate will put one round of effort in, and then take whatever comes next. They are in the position of strength, and ultimately probably have other people to hire if you walk away.
You, on the other hand, may really want and need this job.
A salary negotiation can take SEVERAL rounds of back and forth, can take several days to a couple weeks, and might get people feeling testy and agitated throughout. This doesn't mean something is necessarily wrong, it just means the parties are perhaps further away from agreement than expected.
So give it a shot. Then give it another shot. And maybe another. You'll be surprised at how much you can learn and gain by advocating for yourself.