Unable to create lead from my account

Unable to create lead from my account

Hi i am trying to add lead from my Zoho Account but i get the following message(Sorry,you have reached the maximum limit in your current edition). we are using the free edition up to 3  user but recently we want to see the full functionality and we sign up for professional trail version which is expired now. But before that i was able to create, edit the lead and potentials. is there any want i can go back to normal and utilise ZOHO CRM.