Daptiv Tasks have a minumum Duration of 1 day so if you have a series of 1 day tasks with FS predecessor relationships, then it is not possible to have them occur on the same day.
To set them up properly in Daptiv's Gantt, edit your dependency and set a lead time of "-1". This will put them all to occur on the same day.
It is in our roadmap in Gantt 2.0 to revise our engine to support less than one day duration.
