To set this for the future:
Settings/Transfers/General/Auto Start-Stop/ {x} Start previously running transfers on program startup
To restart them now, from main Tixati GUI:
Transfers/Layout/ set {x} Tab View
Transfers/Layout/ set {x} Sortable View
Transfers/Layout/Categories/ and set {x} Sidebar
Transfers/Category sidebar and select "All Transfers"
Transfers/Layout/Select Columns/Transfers View
enable {x} Progress, {x} % Complete and/or {x} Bytes Remaining then {Close} that dialog
Click on one of the 3 above column headers to cause a sort. If the unfinished torrents are not at the top, click again to reverse the sort order.
Once you have sorted out which torrents are not 100% complete, select any or all of them and click the {Start} button.
Then, IF you did the first step, in the future these will automatically restart to continue downloading.