That happened to me in the past.
Remove the axle, make sure the C clip is still OK, rotate the axle 90° and re-insert it. With all the joints aligned, give it a good push by holding the axle with both hands and using your body as a weight transfer.
If it doesn't go in, rotate it again an additional 90° and try again.
It should work.
Just be careful with the seal, not to damage it.

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