Capital Gain Clarification to my Articles

Please Reply: In the Financial year 15-16{A.Y 16-17} Sold Business Property(portion of land and Building) received 1 flat as Consideration plus Cash Of Rs 50lacs (Total Worth 93lacs) and Long Term Capital gain arises on Such Transfer of 59lacs,Immediately Purchased 2nd new flat for Consideration {2.10 Crores}as Cash Of 50lacs we received earlier paid as payment and Installment 10 lacs..Totally 60 lacs paid for such new flat.So Claimed Exemption on Capital gain u/s 54f...in the F.y 2017-18(A.y 2018-19),He want to Refuse the agreement of New Flat,What is The Consequences for Exemption Taken Earlier,And When it should be Reversed?