With the weapon pointed in a safe direction, flip it upside down so you are looking at the loading gate...
What part of the shell is visible in the gap between loading gate and mag tube?
You should only be seeing the head and rim (a little over half inch of the shell)...
If you see more, push the loading button, and gently see if you can slide the shell back 'forward' into the magazine...If you can move it forward, hold it and then release the shell...It should now look as I described earlier...
There should be no issue whatsoever with loading shells into the mag with the bolt closed...