Sony Vegas transitions away when clip together?

I recently started cutting videos (Sony Vegas) and put together some twitch clips.

Only if I then want to insert a transition between the clips, then it disappears when the clips are together. If they have a small gap in between, it works.

I recommend you to read and understand the manual.

To insert a transition in Vegas, the video clips must overlap.

Then just drop the transition to the overlapping area.