External DVD drive not working on iMac with Mojave

Since the drive claims to be compatible with macOS versions as far back as 10.6, it *should* work out of the box with Mojave. Let’s go through some key checks and steps to troubleshoot this.

Even though it's USB-powered, many of these cheaper drives are underpowered by a single USB port:

• If it’s a single USB-A plug, try plugging it directly into the iMac (not a hub).
• If it came with a Y-cable or secondary USB plug for power, use both ends.
• Try a different USB port on the iMac or even a short, good-quality USB-A cable.

Let’s see if macOS even detects the drive at all:

1. Go to  > About This Mac > System Report.
2. Under USB, look for the external DVD drive. If it shows up here, the Mac sees it at the hardware level. If it’s not listed, there’s either a power issue or a hardware incompatibility.

Next, let's try testing it with a known-good DVD or CD inserted into the drive.

• If nothing happens, open Disk Utility and see if the disc shows up there.
• If it does, but Finder doesn't mount it, check Finder > Preferences > General and ensure “CDs, DVDs and iPods” is checked under “Show these items on the desktop.”

Next, let's try resetting your Mac's SMC.

Ref: Reset the SMC on your Mac - Apple Support

Finally, try using this drive on another Mac or PC.

If all else fails, it's likely that the drive is technically "compatible," but doesn't behave well with Apple’s USB power limits or drivers on Mojave. Some of these budget-brand drives use generic chipsets that are hit or miss. You might want to test a drive based on a known-reliable chipset (like an LG or Apple SuperDrive clone with the correct USB-to-SATA bridge).

Try this:

SMC Reset:

Shut down your iMac.

Unplug the power cable for 15 seconds.

Plug it back in and wait 5 seconds.

Start the Mac.

NVRAM Reset:

Restart and immediately hold down Option + Command + P + R.

Hold for ~20 seconds, then release.

You're very welcome!