MacBook Pro won't auto-power TV extended display

The Mac does not rely on Windows-like side-loaded "Drivers" which are actually packages of resolutions and settings for a specific display. Instead, it goes straight to the immutable source -- it asks the display itself.

To get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.

This query is only sent at certain times:

• at startup

• at wake from sleep — so momentarily sleeping and waking your Mac may work

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• hold the Option key while you click on the (Detect Display) button that will appear in Displays preferences (from another display)

so try doing some of those things and see if the display comes alive.

Modern Displays with multiple ports are sometimes busy scanning the other ports, looking for an input, and miss the query from the Mac. They need to pay attention to the port you are actually using, or they will miss the query.

Some displays have On-Screen Display settings that can be used to tell the display a computer is attached on a certain port, or a certain port should be highest priority. Changing those may make your display more responsive.

Some displays include their own private "sleep" settings for the display alone. This can allow the display to enter its own sleep mode, on top of the Mac's not sending it data. A display that is sleeping on its own can generally not respond to the Mac's query, and will stay dark.

What changed since the last time this worked?

How is the TV connected to this laptop.....to the laptop's built-in HDMI port or an USB-C port?

Is your laptop an Apple Silicon Mac? If so and you are connecting the TV to the laptop's USB-C port, then try changing the Privacy & Security System Settings for "Allow accessories to connect". Try changing it to "Always when unlocked" (may be worded differently depending on the OS) although this may not be enough.....if not, then try "Always". Unfortunately the Thunderbolt security settings for the USB-C ports doesn't always work correctly if it is set to anything other than the two options I mentioned. Prefer the former option if it works since it really doesn't minimize security since the latter option is a security risk when your laptop is unattended especially in public (or if lost/stolen).

FYI, I find a lot of external displays tend to have issues connecting to Macs these days even when I try to force both the Mac to rescan & toggle the external display to the correct input (even power cycling the display). TVs tend to be just as bad, though I rarely connect a Mac to one. Many times I need to connect the Mac to a much older simpler 4:3 LCD display. Now imagine trying to do this when a laptop may have a hardware issue or is not working correctly.

@Grant here is definitely the forum expert on Macs & Displays. You are in good hands.

If the TV does respond to the Mac's Query, it will show up as a listed display.

¿does it show as a listed display?