Mac Pro Won't Recognize TV

Wow you must be so confused with some of the replies here. Acting super knowledgable when you clearly aren't confuses everyone, and is a little selfish if I do say so myself.

ANYWAY.

Have you tried opening System Preferences -> Displays and checking the first tab for your screen and settings for it?

You'll also see an arrangements tab show up if your screen has been detected. Speaking from experience, if the display isn't showing in the Displays tab after plugging it in, the screen is going to be a nightmare to get working. If it is in the settings but isn't displaying, changing the arrangement usually helps.

https://support.apple.com/en-us/HT202351

Oh yeah...don't forget to check your signal attenuation 🤣

Although no maximum length for an HDMI cable is specified, signal attenuation (dependent on the cable's construction quality and conducting materials) limits usable lengths in practice[69][70] and certification is difficult to achieve for lengths beyond 13 m.[71]

from:

https://en.wikipedia.org/wiki/HDMI

If attempting to go a long distance, repeaters may be needed.

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.

This query is only sent at certain times:

• at startup

• at wake from sleep

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

• on invoking Option-(Detect Display) button in Displays preferences

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 cannot respond to the Mac's query, and will stay dark.