Info
It is not possible to change the Playlist type to chained if there is no Playlist scheduled before that Playlist.

Yellow & Red Elements in Playlists

just:play uses color codes to indicate scheduled elements which will only be played out partly or not at all.

Image Modified

Yellow Elements

Yellow Elements will be played out partly. The reasons are:

Another element will start playing before the end has been reached.
The end of the Playlist will be reached before the element has been played out completely.

Red Elements will not be played out. The reasons are:

The total length of all elements in the Video track exceeds the length of the Playlist. This can be avoided by activating the Auto Duration feature for that particular Playlist.
The following Playlist starts before the current Playlist has been played out completely. This can be avoided by activating the Chained attribute for the following Playlist.

Note
Only Videos (and Placeholder items) which will not be played out are shown in red color. The operator responsible for the Channel should take care that such situations are solved before going on air.

...