My Macbook Air M1 2020 cannot detect Dell Plus QHD USB-C Display S2725DC

You could try substituting a high-quality USB-C cable (that is rated for carrying 4K video) for the one included with the Dell monitor.

If Dell included a "lowest bidder" type cable in the box (I don't know if they did), there might be display transmission errors. Modern versions of macOS are reportedly intolerant of those, and may deliberately cut resolution – or signal – when they see such errors. (Other platforms like Windows might not be as picky about errors – and thus marginal cables might appear to work with them.)

If your Mac connected briefly a couple of times with the bundled USB-C cable, that might suggest that the cable is almost but not quite good enough to support an error-free connection. The two times when your laptop "magically connected to the display" might then represent the bundled USB-C cable having an unusually good day.

As for HDMI wires and adapters - if you were using HDMI cables, were they Premium High Speed, Ultra High Speed, or Ultra96 HDMI cables? Standard HDMI Cables are good for 720p and 1080i TV sets and not much more; and High Speed HDMI Cables are only good up to 1080p. If your HDMI cable is not certified, it is likely that it is only good for standard HDTV sets and not for your 2560x1440 monitor or for an Ultra 4K HDTV.

niuniumi wrote:

I just bought this Dell monitor, which is supposed to support MacOS. My laptop cannot detect the display for some reason, but it shows that it's being charged. My siblings both have non-Apple laptops, which instantly work on the display. I've also tried both the USB-C cable Dell provided, and I've also tried HDMI wires via and adapter.

How many external monitors do you have connected to your M1 MacBook Air? That computer only supports one external monitor … so if by any chance, this is a second external monitor, that might explain things.

niuniumi wrote:

I've also tried to do thing about resetting NVRAM or whatever when i googled, but the button combinations don't work for me?? it just restarts my laptop

You probably found an article about resetting NVRAM/PRAM on an Intel-based Mac – or on an even more ancient 68K-based or PowerPC-based one.

Apple-Silicon-based Macs like yours are not set up the same way, and do not have these key combinations. On a M-series Mac, when you power on the system, if it thinks the NVRAM needs resetting, it will do that automatically.

Mac startup key combinations - Apple Support

Dell – Dell 27 Plus QHD USB-C Monitor - S2725DC

Dell 27 Plus QHD USB-C Monitor S2725DC User’s Guide

This is a 27" monitor with a resolution of 2560x1440 pixels, and a refresh rate of 144 Hz.

It has

• A HDMI input with support for up to 256x1440 pixels, 144 Hz variable refresh rate (VRR) as specified in HDMI 2.1
• A DisplayPort input (version 1.4)
• A USB-C input (with support for DisplayPort Alt Mode version 1.4, and Power Delivery of up to 65 watts)
• Two USB-A and one USB-C downstream ports

Dell says that it supports both Windows and macOS. I would not think that any drivers are needed, unless there was something like Dell Display Manager for macOS and some special feature within that that you wanted to use. (I have a different Dell monitor and have never installed the Dell display management application that goes with it.)

The User's Guide indicates that at a resolution of 2560x1440 pixels, the monitor can support refresh rates of 59.95 Hz, 120.00 Hz, and 143.97 Hz on any of its inputs: HDMI (page 16), or DisplayPort / USB-C (page 17). So I'd think that at the very least, your Mac could establish a connection at 59.95 ("60") Hz, whether or not it was willing to go for a 120 Hz or 143.97 ("144") Hz refresh rate.

From what I have read you didn't mention the version of Mac OS you are running.

Some people are saying they're having some monitor issues with MacOS 26.0 Tahoe

but there are lot of people saying Tahoe has been fine for them, it is very new and updates

will fix any issues, I use a USB-C to Display Port cable to a 27" 1440p 180Hz Acer monitor,

running MacOS Sequoia 15.7 on a M3 Macbook Air.

I have iPadOS26 on my tablet and iOS26 on my phone and not had any issues yet.