Control comparison conditions
Keep device, app, route and destination fixed. Test Wi-Fi and mobile data close together, first directly and then through the VPN. Change only the network so a simultaneous route change does not obscure the cause.
Check local access when only Wi-Fi fails
Check signal and any network sign-in page, then test nearer the router. On a router you own, review vendor updates and back up settings before changes. Ask administrators about hotel or work networks. Do not disable Wi-Fi encryption or ignore certificate warnings.
Verify recovery after switching
A network switch can interrupt an existing connection. Wait for the app status to update and load a page to confirm recovery. Record networks, time and errors. If mobile data fails directly too, check signal, data allowance and carrier status before blaming the VPN route.