Haha no, don't connect the resistor across DC+ and DC-. That is rectified mains voltage.

You misread / misremembered the words "Braking resistor is connected between R+ and R- or DC+ and R-"

The "R-" terminal is the braking resistor switch that goes low when the VFD wants to initiate braking. Otherwise it draws no current and should read 330V or so.

What is your decel time set to? If it is set nice and short, the decel should cause the voltage to rise until the braking threshold is met, at which point, voltage should appear across the resistor.