How do we invoke my mother’s health care proxy when her doctor won’t? She is suffering from significant diminished capacity and needs help.

She lives alone, has had two bad falls and now a chronic heart problem. She’s not taking her meds properly and her doctor will not get on the phone with us to discuss her health or screen her for diminished capacity. She has been in the hospital each of the last three months. He has said she is not safe in her own house, but won’t engage with us so we can get her the help she needs. The VNA has said it is obvious she is diminished and spoke to the doctor’s office about her mental state and her living conditions. We have sent him two faxed letters (followed with hard copies) asking for him to engage and no response. When we called the receptionist asking for her to leave a message asking doctor to call us, she hung up on me. I just can’t believe this is happening. My mother is at risk, not bathing, living in horrible conditions and doesn’t remember things from 5 min ago and has now lost her lifeline help necklace that would help her if she were to have another fall. What options do we have to have her HCP invoked? We are shocked as a family that the doctor is not deeming her incapacitated or helping us, She tells us he’s told her she’s fine. She is not fine. Still driving, ran into a parked car with someone in it (third accident), she calls us at all hours of the night-doesn’t remember the next day. Doesn’t remember speaking to us one hour ago. Loses everything. Meds are a mess. We are losing our mother before our eyes and feel totally helpless. I am so incredibly shocked her doctor won’t help us. What do we do?