Factors that cause the low sales volume:

1. Quality
2. Price
3. Brand Image
4. Dealers Profit
5. Awareness about product
6. Competitor’s price
7. Distribution system
8. After Sale Services
9. Customer’s Satisfaction
10. Customer’s use of Product

If price of housing goes up, it is normal to observe decline in purchases of everything related (furniture, appliances, garden tools, etc.)
Strong competition could be another factor.
Major change in consumer's behavior can be a factor, too. For example, new fashion style can affect purchases.
At last, but not least, overall economic misfortunes on macro-economic level can negatively affect sales.