I have to agree with Gonesaleing. Its kind of like trying to shut the pasture gate after the cows have gotten out. As we all know, the spoken word must be weighed very carefully, because it can never be taken back. And sometimes, "I'm sorry" doesn't even begin to cover the damage it inflicts. You started off on the wrong foot with these ladies and it will take A LOT of time for them to forget. We all judge on first impressions, whether we admit it or not, and yours by your own admission, was less than stellar.
While I sympathize with you because I was in your same position of being the "newbie" a few months ago, there is a way to handle things. In all things, but especially PTO, you must be diplomatic. One thing I've noticed is I'm constantly playing the politician to keep all sides happy. In the beginning, we all feel like outsiders and feel that they are speaking over our heads. Thats part of being new. And it is very unnerving. But something I did was I kept telling myself, I'm new, they're not, and I will learn this. And I have. I've gone from "newbie" to being the president next year because I was willing to learn and realized that I had no right as a new member to come in and tell them what they should and shouldn't do. I earned their respect. I didn't demand it.
I don't think it was anything they were purposely doing TO you. They were just conducting business as usual. Up until you stood up and spoke, they had no idea that you had an opinion to voice. Now, while it was rude that they didn't acknowlege you and welcome you, attacking them verbally was not the way to go about making new friends.
Instead of demanding apologies, you must put yourself in their shoes. As you have said, you are the president of a homeowner's association. Imagine if someone new moved into your neighborhood, came to their first meeting, and immediately started telling you that you were doing this wrong, that wrong, and everything in between. And you've never even laid eyes on this person! How would you react? Human nature would be to turn to your friends for support and even rehashing the event. Yes, this person may have only attacked your policy, but because its your policy they're essentially attacking you personally. At least that's what it feels like. I'm sure you would be discussing the situation with others, just as the PTO members did about you.
I would leave the situation alone. You've apologized numerous times, essentially allowing it to be brought to the forefront of their memory over and over again. Move on. You're not letting them forget it! You've done a fantastic job with parent communication. They've let you have your little niche and that could be seen as the proverbial olive branch on their part. They could have just shut you down completely. Don't expect these women to welcome you into their fold and be their friend after you admittedly behaved poorly first off. With the way you keep bringing it up, you're just stirring the pot and putting the principal in an untenable position of trying to keep the peace. The more you keep at, the more they're just going to see you as a troublemaker. And nobody likes a troublemaker.
We need to all remember that this is not about us. Its about our children and our school. Sometimes that gets lost when parents put the focus on themselves, instead of where it should be. We volunteer because we want to make a difference. That's what motivated you to go in the first place. You saw a problem that needed to be addressed and you've taken steps to correct it.
Take a deep breath, get through the year, and begin next year with a fresh outlook and a new attitude. Don't let the last meeting of the year end on such a sour note. Given time, maybe the summer will allow hurt feelings on all sides to begin healing.