cafa69 wrote on Aug 19^th, 2019 at 4:54pm:

How can I uninstall the 757 as if I was moving to another PC so it DOES ask me for the activation key? In other words, to do a CLEAN re-install of the product with no history of past installation?

That won't help.
Most likey you use a corrupted flight.
Delete all saved flights and try default CS flights.