What are three problems with fusion?

As a curious investor in the world of energy technology, I'm intrigued by the potential of fusion as a clean and abundant energy source. However, I'm aware that there are still challenges to overcome. Can you elaborate on three of the main problems with fusion, and how researchers and developers are currently working to address them? I'm particularly interested in understanding the technical barriers, as well as any economic or practical considerations that may be hindering progress.