mac suddenly cant find internet - all the other devices in house can

..Watercolor123..

Perhaps a way around this limitation could be a multiple-step process

where first you could start the iMac (apple silicon) 24" in Safe mode..

There are steps within this by itself; and this is not a destination.

How to use safe mode on your Mac - Apple Support

//support.apple.com/en-us/HT201262

A second similar set instructions for Safe mode:

Start up your Mac in safe mode - Apple Support

The Mac will show evidence of a successful 'Safe mode' startup

and will not use internet or wi-fi to test itself. Restart after iMac

runs up into Safe mode, then re-start it normally. (I usually give

my Macs something to do, an offline task; like repair the drive.

From disk utility within the Mac. You may find this problematic.)

[Where more than one system might be installed, there could be

options to run an Internal version of Recovery; from a partition.

Mine can use these, as it has more than one macOS installed.]

..Another idea to see about Creating an internet connection..

IF you've an iPhone: Set that up, & create a Personal Hotspot

& run a USB cable to the Mac, when Wi-Fi won't go online.

This can be a test, if successful: IF there's no detail uncovered.

And should not require the iMac's Wi-Fi, IF the USB cable is used.

But settings still may be necessary, to make this work backward.

Regular setup Personal Hotspot with Wi-Fi [&/or] Without Wi-Fi (this covers both)

How to set up a Personal Hotspot on your iPhone or iPad - Apple Support

//support.apple.com/en-us/HT204023

(..for reference, above is how the next part below was arrived at..)

Next: Try this ~ Only using USB cable (from iPhone set up) - to supply internet to Mac.

If Personal Hotspot is Not Working on your iPhone or iPad (Wi-Fi + Cellular) - Apple Support

//support.apple.com/en-us/HT203302#usb

This Second part is a Workable idea.

(Your iMac may require AASP or Genius inspection

to help determine what else is truly wrong with it.)

With a USB cable, connect your Mac to the iPhone or iPad that

provides Personal Hotspot. If asked, trust the device.

Make sure that you can locate and view your iPhone or iPad in iTunes or the Finder. 

1. On your Mac, choose Apple menu  > System Settings (or System
2. Preferences), then click Network. A list of network services appears, including Wi-Fi.
3. If iPhone USB doesn't appear in the list of network services, add iPhone USB 

using the steps to set up a network service. 

If iPhone USB appears in the list of Network services:

•macOS Ventura: Click iPhone USB. ~ Click Make Inactive, then click Make Active. 

•Earlier versions of macOS: Click iPhone USB. Click the More button below the list of

services, choose Make Service Inactive, then click Apply. Click the More button again,

choose Make Service Active, then click Apply.

Genius Bar Reservation and Apple Support Options - Apple

//www.apple.com/retail/geniusbar/ Try chat or phone options

to get an appointment for evaluation of hardware + software.

Sometimes a newer Apple Silicon mac may need the system

revived or restored using Apple Configurator, at an Apple

authorized service or Genius..

Revive or restore a Mac with Apple silicon using Apple Configurator - Apple Support

..This idea is likely beyond most home/office users; and should not be needed..

A quality backup to external source (clone?) or complete restore of macOS maybe

needed if this should be necessary; backups, done before storage gets flashed.

Have you added any wifi connected devices to the household lately?

Is it possible you have exceeded some arbitrary allotment of DHCP addresses allowed by your ISP?

Have you contacted your ISP for assistance and troubleshooting?

You might edit the list of DNS servers that your Mac uses to resolves internet addresses and see if that helps.

To change this list on your Mac, choose Apple menu  > System Preferences > Network, select a network service in the list on the left, click Advanced, then click DNS.

If there’s a lock at the bottom left of the Network pane, click it to unlock the preference pane.

With the pane unlocked, click the Add button ( + ) at the bottom of the DNS servers list, then add these DNS numbers to the list:

1.1.1.1

8.8.4.4

8.8.8.8

9.9.9.9

Click OK to continue and then click Apply when you are returned to the Network panel.

EDIT - While you are in the Network panel, edit the order of the service list in the left pane by clicking the gear icon below it, then Set Service Order... and drag Wi-Fi to the top of the list.

Please see: Change DNS settings in Network preferences on Mac - Apple Support

..Could be almost any kind of issue, related to symptoms only..

Use Apple Diagnostics to test your Mac - Apple Support

//support.apple.com/en-us/HT202731

•Change Wi-Fi settings in Network preferences on Mac

•Apple Support article: If your Mac isn’t connecting to the internet over Wi-Fi

•Use Wireless Diagnostics on your Mac - Apple Support

•Use macOS Recovery on a Mac with Apple silicon - Apple Support [macOS13.x]

•Ways to start up your Mac - Apple Support

Depending on the macOS version, 'About This Mac' in Finder

has hardware section to look further into, see what is shows.

How to use safe mode on your Mac - Apple Support

//support.apple.com/en-us/HT201262

..Other ideas come to mind, however the hardware may/not be at fault..

[edited]

Have you done "Forget this network", the network you normally use and reconnected to it?

I suggest you do that.

Might be a problem with the wi-fi system inside the Mac