Monitor button

I have an Inspiron 5400 AIO all in one.  I watch TV on the screen using HDMI and pressing the monitor button to access HDMI. Recently when I press the button to change from HDMI to PC or vice versa, I find it will not change unless I restart he computer, it will then change but only for a minute or two. I would appreciate any help with this annoying problem. I have tried reinstalling windows and have all Dell updates. Thank you.