It is from 2017 which is why I wrote it was in the first sentence of my answer.
Nazanin Zaghari-Ratcliffe has served her original sentence. She was convicted of a second offence which was based on an incorrect statement Boris made to a Select Committee. He told the Committee (and the Iranians) that she was training journalists, not on holiday seeing her family. Based on Johnson’s statement she was convicted and is still in jail.
The additional sentence is not for any crime committed in Iran, it for plotting against the regime in 2013 at protests outside the Iranian Embassy in London. The protestors were photographed by Iranian Intelligence, and a match with Zaghari Ratcliffe was made.