[Koha] Can't tick "item due" box in Patron messaging preferences

Dear all I am trying to send reminders for overdue items. I am currently reading the manual and I think I have got everything, but still I can't tick that box (in an individual patron or in the administration "patron categories"). I can actually tick the box and then I click on save, but it's not saved. Though, if I tick other boxes (Item Checkout, Hold Filled, Item Check-in), it saves correctly and then it's really ticked when I load the patron preferences again... I did the notice triggers, the enhancedmessagingpreferences and I don't remember what else. Cheers, Sonia.