I have nothing displayed in « Background Tasks » on my Gladys, has this happened to anyone? How can I make this data reappear?
Simply because there was nothing: after some time, data arrived…
Sorry!^^
It’s great that you’ve solved your problem on your own 
The « background task » view currently displays data aggregation tasks, calculated every hour. Indeed, after the first installation, you may not have any tasks that have run yet.