Invisible lines won't connect

Have been working with Harmony 15 since last year and suddenly had an issue with vectorial invisible lines (Stroke tool).
They just won’t connect to each other so i cannot paint as they’re not closed, I need to use pencil line, then erase the pencil and keep the line.
I don’t know if some tool property got deactivated because this didn’t happen before.

The screenshot makes it look as if the license are connected.
Are all the lines you drew on the same drawing layer?
Only lines on the same drawing layer can be connected.

Select the pencil tool and go to the “Tool Properties”
make sure the desired options are active, such as
auto gap close and line builder mode if you use this.

Thanks for your answer. It helped me a lot.