in VR if I move HMD, in the floor appear and disappear reflection, is no static like reality, how I fix this?
Is it a screen space reflection? If so, the reflections only reflection what is visible on screen. You can use planar reflections if you want better looking and more accurate reflections that never disappear. But They are more demanding. You can take a look at the project files for Robo Recall to see how they used them and the performance optimizations they used.
I try to activate planar reflections and reboot project, don’t change anything 
You have to put planar reflection actors into your scene too, where you want the planar reflections.