TELEGRAM IS NOT DOWN
Telegram has migrated to 64-bit IDs. After updating Telegram, some users may have to wait a minute or two for their chat database to be optimized for 64-bits, but sometimes Telegram stuck on updating.
If your app is not updated:
1. You can send messages, but won't receive any of them.
2. You can't login using outdated app.
Update your app, or if you are using an outdated unofficial app then switch to the official app. telegram.org/apps
src : tgbeta