Axle shouldn't be this hard to install

It is possible the other axle is holding it from going in. Loosen the other side up and see what happens. If so you need to back the bearing adjuster out on the right side. Always install the left side without the adjuster first. Then back the adjuster out on the right side to install it. After installed proceed to adjust for bearing preload using the adjuster only found on the right side axle.