lost recent apps?

I turned on my phone today like I usually do and all of a sudden when I press the recent apps button at the bottom of the device the words no recent apps pop up and that's it . I didn't do anything different or change anything. I even restarted the phone opened a few apps jumping back to home screen each time just to double check and it still doing it . Does anyone know what may have accidentally got pressed or changed to cause this? The only option I ever remember seeing is in the development section under settings at the very bottom to set the limits of the background apps and the other one below that but I have not messed with them . Thanks

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