Great to hear you solved the issue, no doubt MSFS is playing games with people’s bindings again!
@mdapol is correct, stay out of reheat and AT after take off until 24,000ft and the accel point. Max power, reheats in then and ALT ACQ in the autopilot up to 45,000ft / 50,000ft depending on atmospheric conditions. When you reach Mach 1.7 in the climb, you can turn the reheats off - Concorde will maintain Mach even in the climb and accelerate once leveled off in supercruise.