I’ve had re-occuring issues with Looking Glass Portrait displays where the touch sensitive capacitive buttons (Forward, Back and Play/Pause) would not work. (Either straight out of the box, or intermittently.)
After a lot of back and forth with Looking Glass (and them shipping me 4! replacement units) I was finally able to determine that the issue is the provided CHOETECH USB-C 20W PD power supplies. (Which apparently don’t work well on the 110-113 volts AC at my house, even though they are rated at 100-240 volts AC….)
I’m not sure if it is a power issue, or some type of noise/frequency that the power supply generates when running on voltages close to the bottom end of its range, but I can reliably fix the issue by changing over to using my Google Pixel 4A USB-C PD power adapter to power the Looking Glass Portrait.