I have noticed that it is possible to re-open a closed RedMine issue when using one of the default trackers e.g. the "Defect" tracker. However, it appears that if you create your own tracker, it is not possible to open a closed issue. I believe I have checked "roles and permissions" but feel it is down to the tracker configuration.
Has anyone else noticed this and, if so, how have you overcome the problem?
In Redmine, when you login as admin, you will see Administration menu item, at top menu.
Once you click on it, besides Roles and permissions, which you tried to change, there is Workflows menu item, which lets you change issue transition statuses. It is possible that in your case, for Defect tracker, that issue cannot be re-opened.
Once you click Edit, you will be able to change that, here is how issue transitions look like in my case:
So, in your case, you will have to tick few boxes to allow issue to be re-opened, on your matrix.