Cant screen mirror to a tv whit HDMI

[Rytter]

Hi
When I plug in my HDMI cable and want mirror screens to watch a movie on my TV I just get a picture of my background and in the bottom left corner comes a cog and in the bottom right side there are a lot of dots in a square but no more if I go over to HBO on the phone and start a movie then only the sound comes on the television but no movie only the same pictures that have always been when I start mirror screens
what to do?

[AndrewL]

@Rytter: If you have a Smart TV, have you tried Screen Mirroring wirelessly via Smart View to see if this helps? To proceed, swipe from the top of the Note 9 screen to the bottom and select Smart View from the Quick Settings menu, select your TV from the Available Connections, and you should be good to go.

If the above isn't applicable, please can you confirm what adapter you're using, if any, to connect the phone to your TV via HDMI?

[Rytter]

i am using a samsung hdmi model EE-i3100

[AndrewL]

@Rytter: I see. You will need a USB-C to HDMI adapter rather than a standalone cable to mirror to your TV. It doesn't look like we currently have these in stock, but please check out the link below as a reference point.

https://www.samsung.com/uk/support/model/EE-HG950DBEGWW/

[Rytter]

why new cable? the one i have is also usb-c i can use dex on the computer screen so i can write on the computer, so i should also be able to see screen mirror with this cable?

i fix it by a totel reset to factry 

[Arabianstar]

hi any useful update for this issue please. my s10 + has started to do the same on my second TV which I used the same hdmi to hdmi and the same adapter USB c to hdmi .... I used to have no issues but after a recent OTA update it just shows a dex blank screen as described in the original question.
yes I can screen mirror to my " main TV " via the tvs software etc but I still need this phacilty on my handset.... help please. Thank you for your valued time and assistance....

[Collin3]

I had a similar issue and found a fix. In my case I had enabled developer options in settings and had turned on Force Desktop Mode. Once I turned it off again the HDMI mirroring worked as normal when I turned off Dex. 

See the picture below for how it should look:

[Jameswalter]

Disconnect the HDMI cable from the HDMI Output terminal on the connected device. Reconnect the HDMI cable firmly to the same terminals as before on the TV and the connected device. Turn on the TV and the connected device, and turn them off. Then turn them on again to let the TV recognize the connected device.

Regards,
James