Hello Mritunjay,
As per the official website of VIT,the tentative slot booking begins from 3rd week of March.You should wait till this weekend for the initiation of the slot booking,the delay could be due to the imposition of section 144 of CrPC in various states,espescially of the southern region,due to Corona Virus spread.If you have already applied,then the institute will surely notify you through mail or text about any change in the dates.