There appears there is an issue in which certain Audio-MIDI devices are not detected on macOS High Sierra 10.13.3, with the current Line 6 public driver (v7.6.8). This issue would prevent these devices from being used with a DAW on machines running macOS 10.13.3. All of the following products are affected when used with this version of macOS:
Bass PODxt, Bass PODxt Live, Bass PODxt Pro, GuitarPort, POD HD, POD HD Pro, POD HD Pro X, POD HD300, POD HD400, POD HD500, POD HD500X, POD Studio GX, POD Studio KB37, POD Studio UX1, POD Studio UX2, POD X3, POD X3 Live, POD X3 Pro, PODxt, PODxt Live, PODxt Pro, TonePort DI-Gold, TonePort DI-Silver, TonePort GX, TonePort KB37, TonePort UX1, TonePort UX2, and TonePort UX8
QA had tested all of these devices prior to the release of macOS 10.13 (High Sierra), and everything passed at that time.
We have found that this issue was related to the KEXT implementation, which we already noted in the following article:
https://line6.com/support/page/kb/recording/computer-audio-set-up-and-troubleshooting/macos-high-sierra-1013-driver-installation-change-r879/. Please use the recommendations found there if you run into this issue.