When using a Chromebook, make you are using the Chrome version of the app. Many Chromebooks are able to run Android apps from the Google Play Store. Graphical Analysis and Spectral Analysis are available for both Chrome and Android, and look almost identical when run on a Chromebook.
This is problematic because the Android version of these apps will launch on compatible Chromebooks, but will not see any USB connections. Bluetooth connections may work.
On Chromebooks we have tested we can tell if the app running is built for Chrome or Android from the color of the top title bar. If it is black, it is the Android version. If it is white, it is the Chrome version.
Only the Chrome version, available from the Chrome Web Store, should be used on Chromebooks.
Graphical Analysis for Chrome is available in the Chrome web store at:
Spectral Analysis for Chrome is available in the Chrome web store at: