Since v3.12 the Web WhatsApp Feature is moved to URL Structure
Click to Chat –> Other Settings–> ‘URL Structure’ and select Web WhatsApp in ‘Desktop: URL structure’.
If the Desktop: URL structure is selected as “Web WhatsApp”
Dekstop: Navigates directly to “web.whatsapp.com” ( user can chat from the browser)
If wa.me is selected:
Desktop: For the Desktop URL structure, ‘wa.me’ is the default selection and it navigates to “https://api.whatsapp.com/” or asks to open the Desktop WhatsApp Application.
Video tutorial of Web WhatsApp