Troubleshooting connecting HDMI to Mac

Roccotrejo wrote:

when connecting my Mac air is displaying this: a check button and a “off” / “power” button on red.

I don't think your MacBook Air is displaying that.

It looks to me like you have a "smart TV" that is displaying a screen with selections for different inputs, and for several streaming services. The "smart TV" is displaying everything other than the blank (blue) video behind everything. Including the check mark and the power icon. I don't know why it would display both together, but perhaps the manual for the TV set would explain that.

I don't know whether the blue screen is coming from the MacBook Air or if the smart TV itself, when given "No signal", is displaying that as a blue screen.

Are you sure that the MacBook Air is connected to the "PC" input on the TV, and not to another HDMI input? A HDTV set will often have several HDMI inputs.

Also, check to see whether your MacBook Air is running the TV in "mirrored" mode or "extended desktop" mode. If you are in mirror mode, where the computer is trying to display the same image on both screens, the computer may be trying to force some "compromise" resolution.

Extend or mirror your Mac desktop across multiple displays - Apple Support

I would not trust the Adam Elements adapter.

Get the Apple OEM USBc to HDMI adapter and try that out.

You might want to switch to a lower resolution on your TV and see how that works too.

The MacBook air may be a lower power port than your other computer and will most likely have a different graphics controller to drive pixels.