My iMac isn't recognising my Levro III ebook reader

First step is to always start with the software or device developer's system requirements. I cannot find a web site for Levro but you may have it in their documentation.

If your iMac is running OS 10.12 as shown in your equipment line, that could be too old. It is also possible based on a paucity of information on the internet that this company is out of business and the devices themselves are too old to support modern OS versions.

The chances of finding other users here with experience with the Levro are, frankly, slim.

We may be able to ferret out a little more information on connectivity if you tell us your iMac's SUB-MODEL and CURRENT OS VERSION, both quickly available by doing "About this Mac..." from your Apple menu:

Providing those two pieces of device info in future posts will get you faster responses here for any question because we do not have to ask you a question before we answer.

I will ask our Mods to move this to the iMac forum where you will get more views. The "Using ASC" section is supposed to be for reporting issues with using the forum software, but has become a dumping ground for lost posts, so gets few views.