Hi Colin
I have 5.20 installed in
C:\Program Files (x86)\B4A\Basic4android\
and the usbserial.jar in the "\Libraries\" directory
I have 4.3 installed in
C:\Program Files (x86)\Anywhere Software\Basic4android\
and the usbserial.jar in the "\Libraries\" directory
The lib tab on both apps found the UsbSerial(2.40) file so the app has located them. It's only when you build that there is the error in 5.20 only.