1. Ensure that the you have accepted all of your suggested terms you deem related to the topic:
When you click suggested terms (blue boxes) and turn them into accepted terms (green boxes) inside a topic, those green terms will define the topic. The scores are calculated when some special "sentimental" word is directed towards the topic – which was determined by the terms. Thus, having a wider coverage for your topic because of the extra terms in it will result in having more sentimental words directed at the topic. This could increases your sentimental text counts.
2. Sentiment Scores are determined by sentiments which are pointing to the topics. So the data just might not have topics with sentiments pointing to them.
3. The survey question you are asking could be priming the users not to use sentimental texts. For example, the difference between asking about:
1. Did you like the color? - tends to lead towards yes or no and very unemotional text
2. What are your thoughts about the color? - tends to lead towards open ended and emotional text