Dell C1422H (USB-C Alt Mode DP 1.2, HBR) with 2017 MacBook Pro

That display states that it requires 7.5 watts power (5 Volts at 1.5 Amps) to operate fully, but does not specify exactly how that power is to be supplied.

when using with a mobile phone, they recommend you use a USB-C power adapter in the other USB port.

It is conceivable that the Mac does not supply that much USB power by default. It also can depend on EXACTLY what cable you are using, and how long {about 1/2 meter, over 1 meter}

My assumption is that the Dock provides more default USB power than your MacBooks do.

The manual talks about using with a power adapter, then allowing the excess to POWER your computer.

 menu > about this Mac > (system Report) > USB

for some devices, the USB power available and USB power required is sometimes shown. See if that adds any insight.

Hello EvilAshEditor,

Thanks for reaching out to Apple Support Communities. Upon review of your post, it seems that you are having some issues using a secondary display with your Mac. We can see why you’d want this taken care of, so let us help from here! Let’s start by reviewing the following article which may help: Use one or more external displays with your Mac. If you can make sure that everything is working as expected when using your Dell display alone with the cabling detailed in the article, then that identifies everything as being okay with the Mac and the external monitor.

From there, to look into possible issues with the adapters and connectivity hubs you are using, we advise reaching out to Dell directly to determine which hardware the display will be compatible with.

Please let us know if you have follow up questions, so we can continue assisting. Take care!

I am unable to connect to my 2021 MacBook Pro laptop neither.