The browser works, but one application does not

Steps

Look for proxy settings inside the app. If it supports SOCKS or HTTP, enter the local address and port displayed by v2rayN; SOCKS is commonly 10808 by default.
Disable or account for the app's own DoH, VPN or fixed proxy, which may bypass OS settings.
If the app has no proxy support, enable TUN and inspect process rules, DNS and permissions. Restart the app to close old sockets.
Check whether its domain or connection appears in core logs. No entry usually means traffic never entered v2rayN.

A working browser proves the server and system-proxy path, not that every program reads the same OS setting.

The app produces matching log entries and follows the expected path when TUN or its explicit proxy setting is toggled.

Use the actual port shown in your UI. Do not expose the listener to LAN unless you intentionally configure sharing and a firewall.