check your serial cables first of all- always.

there is no 'standard' connector sex or whatever- or pinouts that should be connected for rs232-

sometimes tx is labelled as rx, sometimes vice versa. sometimes with respect to 'modem' device, sometimes with respect to 'computer'.

the manufacturers of rs232 devices never even managed to use a consistent connector sex to indicate the usage of the serial port either.

is there any other way to control this projector? www? ethernet?