When launching from an Icon on the desktop, right click on the PPro shortcut, select properties. In the shortcut tab, in the "Run" setting, choose Maximized. It will always open Maximized.
When launching via an icon pinned to the task bar, hold down the shift key while right clicking, and select properties, then set the run to max.
If you want something other than maximized, especially if you have two screens, then you can change the default open as normal by dragging out the window to the size you want it to start at, and while exiting the application, hold down the ALT key.
I thought you had it, but it didnt work!
Rather than opening PPro directly. Try right clicking on an existing project file and use "open with". See if that fixes it.