Hello kdsimon, and welcome to the forums
The task here is not to
build 40 Sett Paved Roads, but to
have 40 Sett Paved Roads. If (as I suspect) by 'build over 7' you mean you have 'built over' or 'overbuilt' 7 existing Sett Paved Roads with 7 more, the total number of Sett Paved road tiles within your city will not have increased beyond the 12 you originally had. To complete this quest you will need to have 40 Sett Paved Road tiles in your city at the
same time. Overbuilding existing Sett Paved Roads will never get you to that total.
Hope this helps explain things