NIOS II flash programmer

your entry seems to be correct.

if you run the nios2-flash-programmer, does it print out that it is reading / using this file ?

maybe you need to add the --debug oder --verbose option, see the help dialog what option it is i can't remember right out of my head.

if you still get the same message, check your epcs <-> fpga connection.

do you have the chance to verify with an altera epcs device ? just to see that everything else is correct and the source of this problem is related to your device and or the override file.