automatic inserts started working with the preliminary version 2.1.26 appeared in the selection menu VST Live 2.1.26 Pre-Release is online
and therefore I think the best way would be to remove the automation tracks from the old project and create them again.
Better yet, wait for the next preliminary update, they’ll fix another bug regarding automation. 2.1.27 Bugs - #5 by Spork
And now just check at least one track of the old project’s automation without deleting everything at once.