Endings

Don't pull it! Dragging things in Musescore is usually a bad idea, Dragging a volta just makes it look as if it covers more measures, but it is still attached to the single measure and therefore only takes that single measure into account when navigating the playback order. The red line you see shows you the attachment points.

Click on the volta line to select it and then use CTRL+R to put it back in its default position, then use SHIFT+right to extend it as described in the handbook here https://musescore.org/en/handbook/3/voltas#change-volta-measures. You will need to do that for both the first and second time volta lines.