I am completely familiar with how Engines work and this is not a structural problem. I've looked around and it appears many people are having this issue. I even went into sandbox and tried a stock craft, the problem remained. I uninstalled and reinstalled but the problem remains. I found an old thread were one person managed to solve this problem, but his wording was unclear and I not a pro at the game. It Has Nothing to do with staging. I tried with even one stage. It is a problem within the game and has nothing to do with how the rocket was built. This is what he said... I really need some help, thankyou in advance!
Ranger_Legs Jan 14, 2014 @ 10:35pm
So I just got this exact same problem, and I noticed that, in the resource tab that if I checked "stage only" it stated that I had no fuel tank whatsoever. It did not read zero or full, *it did not show the bar for either fuel"
So I tried pressing the stage separate once more after exhausting all other things I can think of
AND LOW AND BEHOLD THE ENGINE WAS ACTIVATED AND LIT!
and now I can deorbit and land!