This also happens to me, installing drivers through line6 monkey and after installing it still won't recognize the driver.
what i did is:
1. unplugged my POD HD500 from my mac
2. reinstall driver from line6 monkey
3. restart my macbook
4. after restart, i did not run line6 monkey yet, instead i connect my POD HD500 to my Mac
5. to my suprise my mac recognize my POD HD500 in the sound system preference.
6. I run line6 monkey and line6 monkey recognize my POD HD and the driver.
Hope that this fix yours as well
Im using LINE6 POD HD500 to a Macbook macOS Mojave 10.14.6
