I've been trying to perform a WILD for some times and haven't been succesful in any of them...

For what I've understood I should start to feel sleep paralys but I feel like it will never come. It takes about 10 minutes or less to I feel my body starting to "sleep", starting from my hands, my arms and my legs. But after that I stay awake for one hour (maybe more) and don't get almost nothing of Hypnagotic Imagery or Complete SP.

I've tried it last time this afternoon, so I would guess that the problem is that I wasn't in a REM period. Is there anything else that I may be doing wrong?