Splitters take the signal and duplicate the display. So nothing is wrong here.
If you want a second extended display your connection is to a second video card or if your video card supports it, a second connection.
I am running windows 10 on my desktop and I have it hooked up to a TV to have two displays. I am using an HDMI splitter (2 Port HDMI Video Splitter from StarTech.com) but my Windows 10 is not recognizing the second display. The TV displays the same screen as my monitor but will not allow me to "extend" because not second screen is being recognized. Anybody have any ideas about what could be the issue?

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