I thought X-Plane was klunky and unintuitive.
I was wrong.
A real Space Shuttle is something that requires months of preparation to set on the pad and months of training for the crew to operate properly - and it has a very unintuitive interface.
To the degree that we aim to provide a realistic simulation, these characteristics carry over - you won't just be able to start the sim and do anything meaningful with the Shuttle (or even expect it to work) without reading some amount of manual first. And if you have no prior experience with FG, you have picked the very worst craft to learn that part.
If you're after a quick look-around in the cockpit, intuitive controls and a launch ten minutes into your orientation session you're with the wrong simulation - this is a high-fidelity Shuttle simulation with a myriad of ways to make your life miserable if you forget a procedure.
I'm SURE everything is customizable and can be made to operate properly.
This is possible, it is also possible that you're seeing an elusive timing bug (the troubleshooting section of the manual should have some context), but you're not providing any information - I don't know what FG version you installed, I have to guess what Shuttle version, I don't know where you try to start, I don't know what other options you selected - I don't have telemetry, I can't magically guess from 'Houston, we have a problem' what the cause of the problem is, sorry.