It’s possible you downloaded the wrong firmware, did not copy all the files to the .Kobo directory, or copied the files to the wrong directory. Here’s what I did on my iMac (from memory).
Download the firmware zip file for the MK7 Clara from here
https://geek1011.github.io/KoboStuff/kobofirmware.html
The zipped firmware should end up in your ~/Downloads folder. Open a finder window and navigate to your Downloads folder and double click the Kobo-update-4.10.11655.zip file and it will extract to a new folder with the same name. Go into the folder and you will see three items:
\Upgrade directory and subdirectories - Linux boot and kernel
manifest.md5sum - md5 hashes for the \Upgrade directory
KoboRoot.tgz - this is the firmware
Connect your device to your iMac, wait for it to power on if it was off, and choose “connect” on the device. A new device called KOBOeReader should appear on the Mac desktop.
Make sure Finder of Mac is the active app, and go to the top screen menu and select “File”, “New finder window”, or press Command + N. Now from the “Go” menu at the top of the screen navigate down to “Go to Folder” ….or better yet…hit Command+Shift+G.
Type: /Volumes/KOBOeReader/.kobo
This will open the hidden folder on your Kobo eReader where we need to move the files.
Copy the contents of the zip (the three items you extracted) in the one finder window over to the .kobo folder (the other finder window). Wait for it to complete.
Right click on the KOBOeReader device on the desktop and choose eject. Within 10 seconds the Clara shut down and started installing the new firmware. It took less than 60 seconds to install. Then the device booted up again. The new boot up time was a little longer than previous firmware.
Check under settings that your device has the newest firmware installed.