It’s a political decision not a technical challenge that is the reason they do not have a functional weapon. If they decided today to manufacture one, it would take approximately 5 days for them to accumulate the required mass of HEU needed for a weapon and approximately 3 to 6 months for them to fashion the core into a deliverable weapon. Than probably another 6 months to miniaturize it into a warhead that could be usable on a ballistic missile for delivery

It should be noted that even though the article is saying they reached 84% purity it’s being slightly manipulative as Iran did not accumulate 84% enriched uranium which would be the real issue if they did. They have still not gone above 60% accumulated