Please check if the two LED on the multilink are on.
Normally when you have this kind of error is due to the debugger can not low the reset line to 0V, so you need to turn off the target (your board), and then turn-on the board and try to program it.
Are you using a custom board?
you also can force to enter to debug mode by putting the reset pin to low at the same time that the debugger is trying to enter to debug mode.
Regards