Two lines that won't join

In the attached file, the red line is a polyline that had fillet corners run in to it.
The blue line was generated with line/ vertical off the end of the red line.
For some reason, I cannot join the two.
Any idea why this might be happening?

Thank you.

Cosmas
Why don’t these 2 curves join.3dm (121.0 KB)

Hi Cosmas- the red curve has doubled up segments so it is a closed curve… Explode, SelDup, Delete, and then rejoin the remaining segments.

-Pascal

It looks like the red curve was copied in place, then joined to itself, so as it is, it is closed. Explode it, then selDup, then join it all back up.

Sam

Edit - Pascal beats me to the punch.

Interesting. Thank you both: )