If your plot feels flat, STUDY it! Your story might be lacking...
Stakes - What would happen if the protagonist failed? Would it really be such a bad thing if it happened?
Thematic relevance - Do the events of the story speak to a greater emotional or moral message? Is the conflict resolved in a way that befits the theme?
Urgency - How much time does the protagonist have to complete their goal? Are there multiple factors complicating the situation?
Drive - What motivates the protagonist? Are they an active player in the story, or are they repeatedly getting pushed around by external forces? Could you swap them out for a different character with no impact on the plot? On the flip side, do the other characters have sensible motivations of their own?
Yield - Is there foreshadowing? Do the protagonist's choices have unforeseen consequences down the road? Do they use knowledge or clues from the beginning, to help them in the end? Do they learn things about the other characters that weren't immediately obvious?