On some Macs, there is a problem with running Tonebridge as an Audio Unit in GarageBand called the “exclamation mark” bug— when adding Tonebridge as an effect in GarageBand, it doesn’t load up and shows the red exclamation mark instead.
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So, to make Tonebridge Audio Unit work in GarageBand, do the following:

1. Be sure you have both GarageBand and the latest Tonebridge installed on your Mac.
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2. Open GarageBand, wait until the app loads up, and then quit the app.
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3. Open Finder and press ⇧⌘G (command-shift-G). A small window with a text field should appear.
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4. Copy this path: ~/Music/Audio Music Apps/Databases/Tags/ and paste it into the text area, then press Enter. A folder should open, where you will see a long list of .tagset files.
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5. Find the “61756678-66317452-55475442.tagset” file, copy it and paste to any other folder. This is your backup file, just in case, something goes wrong. If there's no such a file, just skip this step.
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6. Download the file that comes with this message, and paste it into the “/Audio Music Apps/Databases/Tags/” folder. Agree to overwrite the file, if prompted.
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Get the file: https://www.dropbox.com/s/pf1xluqy03aoclb/61756678-66317452-55475442.tagset?dl=0 (Don’t worry, it’s 100% safe)
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7. That’s it! Now if you add Tonebridge as an Audio Unit effect in GarageBand, it should work fine.
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Please let us know if this didn't work for you.

P. S. For advanced users, try to run this command in the Terminal app:

sudo kill -9 `ps ax|grep 'coreaudio[a-z]' | awk '{print $1}'`
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This should restart Core Audio which is the main cause of the red exclamation mark bug.
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