Web.WhatsApp.com cannot be reached

When I accessed earlier today on my PC Web.WhatsApp.com which links WhatsApp on the smartphone to PC, a message popped up, saying “The site cannot be reached.”

When I ran Windows Network Diagnostics, I received the diagnostics, saying “Your DNS Server might be unavailable.” I highly doubt that that is my problem. All other websites are working fine.

I wonder whether the problem is lying with Web.WhatsApp.com.