DIYbanter - problems with curtain tracking

hello
I have John Lewis curtains which operate on a pull cord tracking
system. When closed two curtain meet in the middle of a bay window. The
curtain and track were fitted by John Lewis so I never saw how it all
went together.

Last night I tried to close them but nothing happened. I realised the
plastic "block" which sits on the end of the track furthest away from
the pull cords had come of the track. The cord which moves the curtain
was hanging out of the bottom of the track.

I tried to fix it but firstly one curtain opened and the other closed
and then, after a bit of fiddling, both curtain were very stiff to
drawer. I can't figure what I'm doing wrong.

Any advice greatly received. Bella