I was intrigued with SpaceX's flyback booster, so I attempted to build one myself. I built a two stage rocket, with Mechjeb installed on both stages. I launch the vehicle and fly up about 30km and then disengage the ascent autopilot. I manually decouple the two stages. I then set SAS to prograde and fire the second stage engine. (just want it to go straight up and stay out of the way.) I switch control back to the first stage and enable Landing Guidance and set my target to KSC. (I have plenty of fuel.) The booster reorients itself and makes a boostback burn to get on the proper trajectory to land at KSC. Reentry goes fine, it even makes a couple of correction burns, but when it comes to final descent, the engine does not reignite (I have plenty of fuel). The engine still shows "Activated". I've even tried disabling Mechjeb and flying back manually and the engine still shuts down. I've tried keeping a low throttle burn going all the way down and the engine still shuts down as the booster gets in the high pressure region somewhere between 10km & 15km. Any suggestions?
