My iMac is not responding

Is your 24" iMac an Intel 2019 or 2020 model? Or is it a later Silicon iMac?

Unplug the power cable from the back of the Mac for 15 seconds. Put it back in and try powering on again.

If that works, it could be an indication of a failing power supply and the Mac could shut down at any time.

Additionally, try booting into Safe Mode according to How to use safe mode on your Mac. If you can then reboot normally and see if that works.

Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.

If that doesn't work, try booting into the Recovery volume (boot with the Command + R keys held down  - Intel Macs) or  (How to Boot an M1 Mac into Recovery Mode) . Then you have several options: you can run First Aid on the drive with Disk Utility or reinstall the System. The user data will not be affected. But you should have a backup, like Time Machine, of the drive in any case.

olakemi wrote:

Thanks for your help. My iMac 24 might needs services. Because I have tried to pressed the power button for 10sec and still not working.

Check the power cable connections and then see if it will turn on.

If not, then you will need to seek service at you local Apple Store or Apple Authorized Service Provider.

I don't know what you've "been on it for 45mins" but you only have to press the button briefly to power it up.

See: If your Mac doesn't turn on - Apple Support

Hold the power button for 10 seconds or until the iMac shuts off and then restart the iMac.

If it is off and will not turn on, see > If your Mac doesn't turn on - Apple Support

Try powering down the Mac by holding the power button until it shuts down. Then power it back up. Also, plug the keyboard in with the charging cable.

I think we covered that.

dialabrain wrote:

I think we covered that.

Something was a-miss, because I didn't see your posts when I posted.

If you're certain the AC outlet is working and you disconnected any accessories, that would be the next step.

No problem.