Is a Realtor Allowed to Place a Lien on a Property for Earned, Unpaid Commission

I am a Realtor with my own brokerage. I have a valid, fully executed listing agreement and a valid, fully executed sales contract for FULL listing price on a vacant, residential property AS IS with no concessions and a fast closing, as requested by the POA for the owner. Then days before the closing the POA says they are not selling. I've asked why. She only says the family situation has changed. I've asked if I have wronged her in any way with no response. I've asked for her attorney's contract info if she isn't willing to talk to me so we could work this out. No response. I've told her I will be taking legal action. I've researched and I'm still not sure if I can file a lien on the property. I believe someone who came to purchase the collectibles may have made an offer on the property and she's trying to avoid paying me for the commission I have definitely earned. I've worked on this sale that is in my neighborhood for over a year since the brother approached me asking if I could help them get the house emptied and sold for funds to take care of their mother without putting her in a nursing home. I've done all I could to help. I've spent extensive hours talking to this family and my investors, helping them get collectibles sold and get the property emptied and ready for closing. Can I file a lien on the property?