I also think it happened after a windows update, because we have used the function without problem for a long time.
And from one day to the next it no longer works.
When there's an update for PDF24 I have to manually do some actions to install them, so I would have know it happened after an update of PDF24, so it can't be that.
So the only logical thing remaining is a Windows update.
This does however still leave the problem existing and I still hope PDF24 can do something about it.