Problems: Solar flare & radiation resistance. Heat dissipation. Energy (more effective solar panels, for things as close to sun as we).
Partially solved - getting to orbit. And as much as we hate musk, SpaceX might solve it once Starships start flying commercially.
If we would separate energy part out and beam it somehow, we could sit in a body's shadow in some Lagrange point equivalent for a given body system and greatly reduce heat dissipation requirements and suspectibility to solar flares.