You might want to confirm the cabling pin-outs. Is the page switch a DCE device? If so, straight through cabling should be used:
Otherwise, if it is a DTE device, a crossover (null-modem) cable will be needed:
As for configuration, make sure the RealPort profile is configured on the Digi One SP for the serial port and that the COM port on the Windows host is configured with the baud rate, stop bits, character bits, parity and flow control which matches that set on the page switch.