External monitors can't be detected after upgrading to macOS 26.1

My new Mac Mini M4 Pro does not recognize the Thunderbolt connection to an ASUS PA32QCV 6k display.

The Mac Mini came with macOS 26.1. Update to 26.2 didn't fix it. Multiple Thunderbolt 4 cables from different vendors didn't work. Changing Thunderbolt connections didn't make a difference.

Thunderbolt connection to a Samsung 4K monitor (LS32D800) works fine using the same cables. The Mac Mini Thunderbolt ports all work with that monitor.

On the PA32QVC side, the Thunderbolt connection is reported as failed. HDMI connection directly to the Mac Mini works fine.

Since I haven't had the Thunderbolt connection work with that ASUS monitor, I'm unable to determine the source of the problem - Mac or ASUS monitor. Next step is to submit reports to Apple and ASUS.

Bugs can be reported to Apple here:

Feedback - macOS - Apple

I have the same problem. Everything worked fine until i updated to 26.1.

It was working fine on 26 and 26.0.1.

I have the Problem on both Macbook M1 Pro Max and Macbook Air M4.

My Setup:

• Two Dell G2724D connected via DisplayPort-to-usb-c to the Hub
• CallDigit Thunderbolt 4 Element Hub
• One Thunderbolt 4 cable from the Hub to the Mac.
• Note: i am aware of Bandwidth limits with TB4. Therefor one Monitors runs at 1440p@165Hz and the other one at 1440p@60Hz. This setup worked well as mentioned above on older OS versions before 26.1

The Problem:

When both Monitors are connected to the Hub and then i connect the hub (via TB 4) to my mac, the mac lags, then Monitors are black and not recognized and i get a notification from Mac:

Accessory Not Enabled
Unnamed Device
Use a Dsiplayport-capable cable and port to connect the accessory

When Only One Monitor is connected to the Hub, No Problems.

We need a solution for this!

LF523 wrote:

My new Mac Mini M4 Pro does not recognize the Thunderbolt connection to an ASUS PA32QCV 6k display.

Update to 26.2 didn't fix it. Multiple Thunderbolt 4 cables from different vendors didn't work. Changing Thunderbolt connections didn't make a difference.

Thunderbolt connection to a Samsung 4K monitor (LS32D800) works fine using the same cables. The Mac Mini Thunderbolt ports all work with that monitor.

Recommended high quality cables: labeled certified ULTRA HDMI or PREMIUM ≤ 1.0 m length

or USB-C Thunderbolt5 cables ≤ 0.5 m length cables rated for high speed data.

I now have successfully connected the Mac Mini M4 Pro to the ASUS 6K monitor (PA32QCV) via Thunderbolt. Using your advice, I replaced the 1 meter TBT4 cable with a Cable Matters 1 meter TBT5 cable. After manually switching the monitor to Thunderbolt connection setting, the display connected and displayed properly in a few seconds.

I then daisychained the Samsung 4K monitor (LS32D800) to the ASUS monitor - immediate success. I used the same Cable Matters TBT4 cable that previously [successfully] connected the 4K monitor to a TBT5 hub.

Subsequently, I tested a TBT 5 cable from an OWC Thunderbolt 5 hub (OWVTB5HUB5P) between the Mac Mini and ASUS 6K monitor with success.

Using a Treedix USB cable tester, the ASUS(?) cable [750.0A50D.0001] with the TBT 4 connection housing labels is *not* identified as Thunderbolt 4. It is identified as USB3.2/USB 4 Gen 2 (10Gbps/20Gbps).

My thinking is that the Thunderbolt connection of ASUS 6K monitor to Mac Mini may be finicky with respect to the cable. A possibility is also that I have an out-of-spec or incorrect TBT4 cable. BTW, in each of my tests, I ensured the cable ends were securely seated in the connectors. Since I have the desired Thunderbolt daisychain configuration working, I'll get back to real work and leave additional experiments to others.