Press and hold the power button for 5 seconds.

There are complete instructions on how to do that in a PowerMax article called “ Two Great Go-To Fixes for a Temperamental Mac” that covers different model machines, but the process for an iMac is as follows: If you don’t have a USB mouse, or if the above doesn’t work, reset the SMC. At that point, you can release the mouse button, log in, and insert a disk in the drive. You should hear the optical drive perform one full eject cycle.

Keep the mouse button held down until you reach the login window. Once the machine is powered off, hold the left mouse button down and re-power your iMac. Shut down your iMac by choosing “Shut Down” from the Apple Menu in the upper left corner of your desktop. If you have a USB mouse connected to your computer, try to reset the optical drive’s eject mechanism first.

I ejected the CD I was just using and now the drive won’t accept anything. I can not get the optical drive in my iMac to accept a CD or DVD. Home » askjacob » Optical drive in imac not accepting cddvd ASK MAX: OPTICAL DRIVE IN IMAC NOT ACCEPTING CD/DVD

My mac dvd drive ejects discs