In order to make sure your old projects (pre-2018) can generate the permitting documents offered in the January 2018 Update, you will need to add a mean roof height before configuring mounting hardware.
To begin, go to the project page of the project for which you would like to generate new documents and permit packages. Navigate to the Roof Properties editor. The icon is indicated in the screen shot below.
You will know the current Mean Height from the listing under Roof Properties.
Type in the correct Mean Roof Height for your project. Then save your changes at the bottom of the page.