We have discovered 315's with the version 6.5.0.0 will not show up in the conductor running 8.10.0.1. Work around is to do the following from the serial port of the AP. Also the serial port for the 315's are a 4 port adapter to USB (hard to find the right one)
setenv master x.x.x.x
saveenv
boot
after upgrade
purgeenv
saveenv
boot