This is actually an nVidia issue, not Overwatch. They have it posted all over the forums when you search for it on Google. The solution they offer is:
restoring the settings in the NVIDIA Control Panel → Manage 3D settings and then rebooting fixes the issue.
Also, make sure to login with your nVidia username and password for the GeForce experience, and not Facebook or other social media, as this also causes the problem.