Belkin Thunderbolt 4 dock not recognizing two external displays on Mac

Belkin – Thunderbolt 4 Pro Dock

This dock has three places where you can connect displays: two HDMI ports, and a Thunderbolt daisy-chaining port. That could be the problem. Macs only support connecting two displays to a Thunderbolt dock, so it is very likely that this dock is getting the extra output using the equivalent of DisplayPort MST daisy-chaining, something that Macs do not support.

You may need to experiment to see if there is a particular set of outputs that will work. E.g., if you are using both HDMI ports now, try connecting one monitor to the Thunderbolt daisy-chaining port (with a USB-C adapter) instead.

Note that if your 14" MacBook Pro is one with a plain M3 chip, it can only drive one external display with the lid open; you must close the lid if you want to use two external displays.

OOPS

The Belkin CONNECT→™ Pro Thunderbolt™ 4 Dock, INC006 is designed to work with Mac® computers that are compatible with Thunderbolt 4 and have a video-enabled USB-C® port. 

NOTE:  It is recommended to use the Belkin INC006 with a Thunderbolt-enabled laptops manufactured no later than the year 2019 for best compatibility. 

• Mac computers with Apple® M1 chip only support a single monitor [with this Dock]. For more information on the Apple M1 chipset, please visit the Apple website at https://apple.com/mac/m1/.
• Intel®-based Mac computers support dual monitors using the HDMI® and USB-C video adapter to get an extended desktop.

NOTE:  Connecting the monitors of Intel-based Mac computers using the two HDMI ports will only mirror your desktop.

https://www.belkin.com/support-article?articleNum=318853

that Belkin dock does not appear to be a good choice for this use.

exactly what model Belkin Dock?

The Mac only allows ONE display on a port, except when the Port, the Cable, and the first device (Dock or Display) are all genuine Thunderbolt. USB-C has far less capacity due to its lower speed, so it will not suffice.

The lead-in cable for the Thunderbolt dock must also be 0.5 meters of shorter for reliable high-speed operation. The cable shipped in the box may not be sufficient.

Windows has no standard for what is acceptable video quality, so your Dock may work fine on Windows.

Grant Bennet-Alder wrote:

OK, I stand corrected.

But do you think this figures into the equation:

NOTE:  Connecting the monitors of Intel-based Mac computers using the two HDMI ports will only mirror your desktop.

That might be true of Apple Silicon Macs as well. It seems like every time that someone mentions a Thunderbolt dock that has more than two places to plug in displays on these forums, it's because they're having exactly that problem.

As if the docks drive the extra output in some way that Macs do not support.

Grant Bennet-Alder wrote:

Mac computers with Apple® M1 chip only support a single monitor [with this Dock].

That's a reference to the limitations of Mac notebooks with plain M1 chips. If the OP is correct in identifying their MBP as a 14" model, it wouldn't have a plain M1 or M2 chip, though it might have a plain M3 or M4 one.

OK, I stand corrected.

But do you think this figures into the equation:

NOTE:  Connecting the monitors of Intel-based Mac computers using the two HDMI ports will only mirror your desktop.