This “waterproof paint” coating is not pretty. It is supposedly to stop moisture from rainwater being absorbed by the concrete tiles but is of minimal benefit long term. Its appearance will put off many buyers. It restricts ventilation and can cause condensation and related problems in the roof space.
The paint is now peeling off badly. It conceals at least one broken tile. Retiling is needed.
The cost of the work will be added to as none of the tiles are suitable for re-use.