@fernandito1969 Hi, sorry for the slow reply. Concorde is a very finely balanced aircraft and as such, it is not easy to fly her correctly ( even though this is not a study-level aircraft ). One of the most important factors is the Centre of Gravity control, which requires you to pump fuel either forwards or backwards through the aircraft as speed increases or decreases in order to maintain balance. Without that, Concorde will not reach Mach 2 or 50,000ft.
In addition, the aircraft weight will tend to hold Concorde back if you attempt to climb too quickly. If you are reaching FL 400 and she doesn't want to go any higher, simply level out and allow Concorde to accelerate. As fuel is burned off and Concorde gets lighter, you will be able to "creep" climb slowly ever upward. Concorde often only reached her highest altitudes towards the end of a flight, and never at the beginning.
Finally, some third-party weather programs seem to interfere with Concorde's flight model. If the above does not help you and you have extra weather programs installed, try switching them off to see if it helps Concorde's performance