2016 MacBook Pro not outputting 4k/60hz on a 4k monitor

RE: 4 thunderbolt 2016 13" MacBook Pro running Monterey

HDMI:

That Mac has no built-in HDMI port. So the resolutions attainable depend completely on the adapter used AND the quality of the cables. The 'shipped in the box' cables are usually 'lowest-bidder' cables, and are inadequate.

HDMI cables you want for HDMI-only Monitors (higher resolutions than 720p TV sets) are marked as Certified with an anti-counterfeiting tag and are labeled:

"Premium High Speed HDMI cable" or that + "with Ethernet" --OR--

"Ultra High Speed HDMI cable" or that + "48G"

Cables with No Certification tags are good for your standard 720p TV set, and not much more.

Displays Preferences shows SCALED resolutions. These are NOT the Hardware resolutions you display is set to. These are effective resolutions for TEXT when displayed on that display when you select Scaled.

They are intended to be a convenience for you, but they often cause concern and outright alarm instead.

To see the ACTUAL resolution your display is set to use:

 Menu > about this Mac > (system report) > Graphics & Displays

Select your display and scroll around until you see two items.

The first is self explanatory: 'Resolution:' 2560 by 1080

This is the hardware resolution at which your display is operating. Graphics are drawn at this Actual Resolution. But there is a problem -- If text were displayed at the Actual Resolution, on HiDPI displays, it would be microscopic and unreadable.

The second resolution shown is 'User Interface Looks like:' this reveals the apparent size of text displayed on your display after scaling is applied ONLY to textual items.

Text is rendered at full resolution, then SCALED by the display Hardware by a factor (like 1.2 or 1.5, or 2.0) before it is aded to the display buffer. This makes it fully readable, yet maintains crisp edges that would be lost otherwise.

Hi Snogglewumps, We appreciate you reaching out to us. We understand that you are experiencing issues the resolution you want on your MacBook Pro.

We’d like to gather additional details that may help us be in a better position to assist you.

You managed to get your preferred resolution on a newer MacBook Pro, is that correct?

In the meantime, we recommend that you check if the issue persists when signed in on a different user account on the affected MacBook Pro. 

The article below can help if you do not have any other user account to test with.

Set up users, guests, and groups on Mac

If you are experiencing the issue when signed in on a different user account, we recommend that you check if the issue persists while on safe mode. 

Below is an article to help guide you through the process.

How to use safe mode on your Mac

Take care!

DisplayPort:

DisplayPort 1.2 does not appear to have enough bandwidth to support hi-color "4K" at 60 Hz.

DisplayPort 1.4 features higher link speeds and adds Data Stream Compression, but the display must have the compute power to do the de-compression or it will not report it is DisplayPort 1.4-capable.

4 thunderbolt 2016 13" MacBook Pro running Monterey

uses older graphics chips, which we talked about at length in many older posts. They were clearly not as capable as later chips.

My notes say that those older chips could not support display wider than 4096, under any macOS.

Yours is not above that limit, but you may have found another limit in the ability of that older graphics chip to run really wide displays.

---So the answer may turn out to be: "Because that MacBook Pro is older and less capable."

sorry, I read the tables on wikipedia wrong.

DisplayPort 1.2 supports HBR2, which provides 17.28 Gbits/sec over the four data lines.

at 10 bits/pixel, that can run "4K = 3840x2160" at up to 65 Hz.