What happens if property tax lien buyer doesn't pursue deed

[Patricia Bates]

There is a property that I am interested in that has been vacant for quite some time located next to my parents home.  It was purchased by a tax buyer in 2016.  They paid 2017 and 2018 taxes but nothing since then.  Do they have a certain amount of time to apply for the Deed and if so how much time?  Can someone else purchase the subsequent taxes?  The property is located in Cook County Illinois