HELP!!!

[Lisa-Michele Smith-Franco]

I placed 2 apartment complexes under contract with the owner and assigned both of them to a buyer whom I had done business with before. He took so long in the deal that the buyer chose not to renew the contract on one of them. The other one did close but I was to be paid at the second closing, its been 8 months now and no communication from the buyer. I try to contact him and he does not respond the last response was an email specifying he would call me when it closed. What are my options in this? All responses would be greatly appreciated!