If you haven't known how Corporation works, it's very simple.
Construct the Corporation HQ to develop Corporate Offices. Corporate HQ in that only one city gets bonuses from Corporate Offices. Corporate Offices get developed as buildings in the Corporate HQ's cities. Corporate Offices get their bonuses from the franchises. Corporate franchises get developed in foreign cities from cities with corporate office's trade routes. But what do Corporate Franchises get? Nothing. Franchises should at least grant +1 Respective Yield to their monopoly resource should the foreign city have it.
Construct the Corporation HQ to develop Corporate Offices. Corporate HQ in that only one city gets bonuses from Corporate Offices. Corporate Offices get developed as buildings in the Corporate HQ's cities. Corporate Offices get their bonuses from the franchises. Corporate franchises get developed in foreign cities from cities with corporate office's trade routes. But what do Corporate Franchises get? Nothing. Franchises should at least grant +1 Respective Yield to their monopoly resource should the foreign city have it.