MacBook Pro not sending signal to Dell monitor via Belkin docking station

USB-C/ThunderBolt-3 signals for a display are generally NOT passed through a dock, except to a Thunderbolt Display. You usually have to fall back to one of the other display ports provided by the dock.

Your situation is complex. If you would like to examine this in detail, Readers would need the exact make&model of each device, and which displays adapters and cables you are using.

One thing I see right away -- the Dell display has a DisplayPort IN and a DisplayPort OUT. You must be certain to plug into the correct one, to get the signal IN to the display. The second DisplayPort will have Drivers, not Receivers, and can not possibly accept the signal coming from the computer.

It does not explicitly say that the display's USB-C port is available as an input. In most cases these are USB-C Outputs with Charging capability.

That DsiplayPort-DisplayPort cable would probably have to come from the DisplayPort OUT of the Dock.

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.

In order to use the USB-C port on the display as an input, the signal MAY have to come directly from the computer.

The Apple ThunderBolt-3 to ThunderBolt-2 adapter, for example, does not provide a usable display signal (except direct ThunderBolt) of any type. If you want a direct display signal, it must be created at the computer port.

One of the horrible problems is that "USB-C" is the name of the connector, ONLY. There are several different things that might be carried by the many varieties of cables with USB-C connectors on each end. The classic counter-example is the Mac charging cable, which has only charging conductors, and reluctantly, USB-2 [suitable for keyboards] (because USB-2 is required to negotiate higher charging rates and voltages).

Your Dell displays can provide charging power for your MacBook Pro when connected directly to a USB-C port. So plug one display in there.

Plug the second into the DisplayPort on the Belkin Dock.

Any more ports you need can be found on your Belkin Dock. You should not need a USB-C port on the computer free.

If you travel, use the supplied power adapter instead of a dell display to provide power.

Readers will find your posting here by searching with google and other search engines (after tomorrow) for a long time.

Can you help the next guy by posting a summary of the way you cabled it up so that it worked?

Thanks!

<<... no idea how to change the displays to extended mode rather than clone on those screens.>>

turn off "Mirror displays" in

System preferences > Displays

.