Need help with French Press Plunger : Coffee

Hi,

I recently bought a french press, I went to clean it and took it apart. I now have an issue where the silver “spacer” (dont know the actual term, the bit that screws the filtering part down) wont go back on, what can I do?

I mean the thing he picks up at 2:45 in this video https://www.youtube.com/watch?v=rGLKTtJAxb8