Your objects have attributes that don't work.
Specifically: the line has the fill rule "Even odd", which the pathfinder doesn't like.
Which is kind of weird - I have tried it in version CC2017 which already showed the same behaviour.
In order tosolve this, you can either use the attributes panel or just reset the objects to the default appearance by using the D shortcut.
WOW thank you !
I did not notice that some of the attributes were ticked.
thank you again
I only noticed because the target symbol in the layers panel was suspicious.
I'm not sure if this is set up in the New document profile you used - "Web"? Would need to investigate further.
If so, you should edit it, because it will happen again.