Can you try to hover your mouse over the three progress bars in the objectives? That should tell you what cures count towards the goal.
I don’t think you have to run the lines with maximum efficiency to have it count, but maybe the cures have to be all exported at the same tick. If that is the case, delete the last belt in front of the export slot and let the last three lines back up a bit, then replace the belt.
That was silly of me, I never pressed continue on Expert and needed to scroll down to see it.
Playing for other 4 cures with the progress bar locked because of that: