Troubleshooting external monitor set up with Mac book air

Your post seems to indicate that you are still trying to use a DisplayPort to HDMI adapter in reverse – something that simply won't work.

Substituting

Computer --- USB-C to HDMI --- HDMI to DisplayPort (in reverse) --- DisplayPort input on monitor

for

Computer --- hub with HDMI port --- HDMI to DisplayPort (in reverse) --- DisplayPort input on monitor

does nothing to fix the problem. All that you did was to change out some of the parts of your configuration which probably were not the source of the problem!

If you want to run a cable to the DisplayPort input on your monitor, you will need to go

Computer ---- USB-C to DisplayPort --- DisplayPort input on monitor

Computer ---- hub with DisplayPort output --- DisplayPort input on monitor

or the like.

Hi there

Please try this

• Reseat cables: Unplug all cables from the Mac, the Acer USB-C hub, and the NEC AccuSync monitor, then plug them back in firmly. 
• Check monitor input: Use the buttons on your NEC monitor to manually select the active input source (such as DisplayPort) instead of relying on auto-detect. 
• Remove intermediate adapters: Chaining a DisplayPort cable into an HDMI cord using a passive adapter or passing through a multi-port hub often fails due to signal conversion limits. A direct single-cable solution (e.g., USB-C to DisplayPort) is much more reliable. 

Adjust Mac Settings

• Detect displays: Go to Apple menu > System Settings > Displays, then press and hold the Optionkey to see if a Detect Displays button appears. Click it to force your Mac to re-scan the ports. 
• Restart the Mac: Perform a full system restart while the monitor is plugged in to clear out temporary display cache states. 

sengeb wrote:

I have a 13" mac book air, M5 that I am attempting to hook up to a NEC AccuSync monitor. I have the display port plugged in, with an HDMI cord between that and an Acer USB C Hub. No signal is detected by my mac or by the monitor. What are my troubleshooting options?

It is not clear how your monitor is connected.

Are you saying that you are using a DisplayPort to HDMI adapter cable in reverse, with

• the HDMI end of the adapter cable plugged into a HDMI port on an Acer USB-C hub, and
• the DisplayPort end of the adapter cable plugged into a DisplayPort on the NEC AccuSync monitor

??? If so, I would not expect that to work. Such adapters are usually one-directional: they go from a DisplayPort source to a HDMI output.

Which specific Acer USB-C hub do you have?

Which specific NEC AccuSync monitor do you have?

(ignore)

I bought a HDMI to USB-C to test the theory that it was due to signal conversion limits from be plugging it into a multi-port adaptor

"Troubleshooting external monitor set up with Mac book air: I have a 13" mac book air, M5 that I am attempting to hook up to a NEC AccuSync monitor. I have the display port plugged in, with an HDMI cord between that and an Acer USB C Hub. No signal is detected by my mac or by the monitor. What are my troubleshooting options?"

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Connecting an External Monitor to your Computer:

It's a matter of equalling out the wattage. Though the monitor is not the same, here is how to connect a 30" Apple Cinema Display to a USB-C-only Mac. See my User Tip: Configuring a USB-C Only Mac with a 30-Inch Apple Cinema Display - User Tip

This is the display port that plugs into the back of the monitor and one end of the HDMI cord

Still getting no signal messages on monitor. I have tried holding the option key on the display menu and nothing pops up. I have tried restarting the computer with everything plugged in