When an audience is unresponsive to your hearty, "Good morning, everyone!" please avoid the temptation to say in an even louder and enthusiastic voice, "Let's try that again. Good morning, everyone!"
While such an approach might serve teachers who have positional authority over kids, it won't work for you because you have to earn authority with adult audiences.
Rather than correcting your audience for their indifferent response, take responsibility for their experience. It's not their job to be interested. It's your job to get them interested.
Likewise, remember to strive for the golden mean.
When threatened, a possum contracts into a ball of submission, while a bear stands on its hind legs to make itself look dominant.
When you feel threatened as a speaker, try to avoid both extremes. If you contract, your ability to inspire confidence diminishes. On the other hand, overdoing it is no good either. Audiences don't like to be dominated.
Strive for the golden mean: high energy, low tension, and a relationship with the audience that is based on equality-not dominance or submission.