If all else fails, slew "Y" up to around 10,000ft (by F4) and then hit Y again and the aircraft should start to descend plus the engine should start. If it doesn't check Shift 4 for consumables and Shift 7 (follow the instructions to bypass the block) and see what condition you are in
First tow the plane into air and attempt a flying start (literally)... then check if you have fuel. Nice. [trollface.jpg]
How about the typical settings in FSX? Like disable engine damage (because accusim has it's own), disable auto-mixture, disable this and that, enable this and that, set full realism, etc. I think the proper settings were all in the read-me so here's the point when it's good to double-check every FSX setting to be what it should. Once you've checked all the settings to match with recommended settings try it again. If it doesn't work, try auto-start.
If auto-start succeeds, then the start up procedure was simply wrong. If it fails, and if there's fuel in the tank (try SHIFT+4 for Accusim consumable manager instead of FSX fuel and payload manager), you've got some problem with the setup. (If everything is empty in SHIFT+4 window or if SHIFT+7 shows all red, and the situation doesn't correct itself by reseting (or restarting FSX) you have a persistent bug (possibly related to installation).
Is the installation order critical here? With many A2A products, installation order is important: first the aircraft, then accusim, then patches (in the correct order if several). You installed Spitfire on SP1 FSX. Because it should be uninstalled and reinstalled again, now that you have SP2? (Before you go through such trouble, at least try to change FSX realism setting to recommended, refuel and auto-start. Because is that actually starts the engine, the problem is only within your start-up procedure.