In order to solve this issue, please try the following steps:
Pay special attention to the four corners of the phone, double-check that the phone has been fully installed in the Vitros case.
If there are no changes, please remove and reinstall the case. Place the bottom of the phone first into the Vitros and then pull the case over the top of the phone.
Using your thumbs push down on the back of Vitros (while on your phone) to squeeze out any air that may be trapped.