The correct course of action for the installers after determining that a scaffold system is the best choice for accessing the roof of the 3-story house would be to set up and install the scaffold system. This involves assembling the scaffold structure securely and ensuring it meets safety standards and regulations. Once the scaffold is in place, the installers can safely access the roof to proceed with the installation of the solar PV system. Ensuring the scaffold is properly erected and stable is crucial to ensure the safety of the workers during the installation process.
I hope this helped!
~~~Harsha~~~