There are so many reasons this might be the case, but it may be worth you booking a 1-2-1 so that we can talk this through. In most cases, this is related to confidence and knowledge. Some people have difficulty selling because they have not followed the team's most important selling rules. The most important of these are as follows:
People, not products - concentrate on the relationship and do not sell too soon.
Give value first - often, this results in your prospect asking for the sale rather than you having to do so.
People hate to be sold to but love to buy - Create an environment where people want to buy; overt selling is not the best option.
All that said, there are so many things we need to consider, so I urge you to book some time for a 1-2-1.