Pretty sure it isn't your TV, if it was you wouldn't have an image on your TV that comes from your Computer. If you are seeing the computer screen saver on the TV it is receiving a signal.
If you have multiple places that the HDMI cable can be plugged into your Computer try switching the cable to the other one most video cards have two HDMI ports. Did the images swap on the TV and Monitor? This is a pretty safe test because you can just switch them back if it doesn't display correctly.
Next
Go into Display Settings by right clicking on your desktop.
Have it "Detect" the screens available to use.
Click Identify and see what number your Monitor is.
Scroll down and select "Duplicate these devices".
You should see the same thing on both screens.
If you don't, try the setting extend these displays and see if anything happens.
If you are still seeing the same thing on your TV but not your monitor for some reason one of your HDMI connections isn't responding to the settings.
Update your video drivers to the latest ones.
Search for "My 2 HDMI connections on my computer aren't displaying the same thing?"
I've never seen that happen, so I have no idea what's going on.
Mike