CTRL + Q is a read (XON/DC1)
CTRL + R starts the write mode (DC2)
CTRL + T stops the write mode (DC4)
CTRL + Z rewinds (SUB)

you have to center the mode switch for it to accept commands

in OFFLINE it ignores everything but manual control and in BINARY
presumably you manually controlled it and it listens for port data,
ignoring any commands given over serial