The message “Your rendering device has been lost.” is Overwatch’s unique error message of when your graphics card shuts down during Overwatch’s operation. There are wide variety of causes behind this. First if you use a NVidia RTX 20X0 series graphics card, there is an ongoing issue that can result in this error. Thankfully there is a workaround solution available until they can completely fix this problem.
If you do NOT own a RTX graphics card, DO NOT attempt to use the workaround solution listed above, instead please follow these standard troubleshooting steps:
If these steps do not work and you need more assistance please post in the technical support forum for further assistance.