I've been flying the 737 for quite awhile, but something seems to have happened to the model. Now, no matter what I do, the plane keeps stalling on takeoff. I set the FMC correctly, with speed bugs in place. It reaches V1, VR and then V2 on the roll. But, it won't lift off the ground. Even when I set the stabilizer trim all the way up, nothing works. In fact, the plane won't lift off regardless of the length of runway, or speed of the 737.This has never happened before. I've had many normal takeoffs until now. Any ideas?

check your joystick, make sure it's enabled and that the null zones and sensitivities are set correct

also check your trim.. it frequently loads from startup with too much nose down and must be set to about 5.5-6.0 deg for smooth rotation.