Hi @Caroline ,
Others should have access to the issues in order to get statistics. That might be the problem.
On the other hand for a more powerful status time reporting you can try Status Time app. It provides various status time reports. Once you enter your working calendar into the app, it takes your working schedule into account too. That is, "In Progress" time of an issue opened on Friday at 5 PM and closed on Monday at 9 AM, will be a few hours rather than 3 days. It has various other reports like assignee time, status entry dates, average/sum reports(eg. average in progress time per project).
Here is the online demo link, you can see it in action and try.
Hope it helps.