Some people are just not ready to hear what you have to say or to receive what you do for them. They always want more or keep on talking even when no one is listening.
Do not let these people steal your power! You have done your best and yet they are still not happy. This just says that it doesn't matter what you do, give or say to them, nothing will change their opinion of you. They are so much into themselves and their issues that they cannot see past their noses.
Walk away and find yourself. You do not need to have the approval of anyone else to know that you are a worthy human being. You wake up and take a breathe every morning and a new day begins! And with that you have the opportunity to be happy as you and not what others see you or don't see you as. You are not invisible and as long as You can see who you are, the others don't matter.
You will find that as soon as you start to follow your own path and actually be You that other like people will find you and you will have new friends. These fellow beings have had similar situations like you, feeling invisible, and that is why you have found each other. You will each be patient and listen to what the other has to say. Waiting for them to finish a thought they had and making comments yourself.
So stop being invisible and find yourself, the true You! Live your life to the fullest, loving yourself and growin stronger each day. Namaste