Many flood lights can be hard-wired for a manual mode, but it doesn't look like this model is configured for it. Ultimately, you can bypass any motion sensor, but it may require modifications that aren't practical, such as in this case.

Just to make sure you're following the instructions for this unit - start in the 'On' position. In less than 2 seconds, turn 'off-on-off-on'.

If that doesn't work, it might be easiest to just swap it with a non-sensored fixture. They're pretty cheap (~$20).