There's a high chance that it's either corroded, or twisted.
When they're twisted they are difficult to put upright. Normally caused by pulling the bike towards you as you do the manoeuvre.
You will not really see if it's twisted until you remove it though.
It's very easy to do, don't be afraid of the spring.
Loosen each side first, then remove one bolt and it will literally just come loose.
Then to reinstall, put one bolt on, attach the spring, then pull the other side into place.
Don't even think about trying to remove the spring first, 'cos that just ain't gonna happen.