When I try to select with the tool, no dotted line comes up. In other words the selection is visible when I'm dragging it, but as soon as I stop it disappears.
There is no such thing as a "Selection Tool" in kde.org You probably want to open a new bug against the proper Product.
Reassigned assuming you are using Krita. If this is the case, please add: - Krita version you are using - Operating system type and version - Exact steps to reproduce If you are using a different KDE application, please specify which.