Windows desktop app's sidebar icons vanish, conversations empty, and login button does nothing after logout (browser works fine)

I cannot log in to the ChatGPT Windows desktop app. When I click “Log in”, nothing happens. No browser opens, no error message appears, and the button seems unresponsive. The same account works normally on chatgpt.com in Chrome/Edge. I have tried: * Reinstalling the ChatGPT Windows app * Resetting/repairing the app in Windows Settings * Restarting Windows * Testing VPN/proxy on and off * Checking that web login works Device: Windows PC Region: Singapore Plan: Plus Date/time: June 27, 2026, Singapore time