Why my connected bot stopped working?

Probably, you’ve revoked the bot token or tried to connect your bot to another service. To reconnect your bot, go to @LivegramBot, send /mybots command, choose your bot from the list, choose ‘Disconnect Bot’ and confirm the action. Messages and bot statistics will not be deleted.

Then send /addbot command and forward/copy your bot token that you received earlier from @BotFather.