Unable to use the bot

Hello, Good Morning

Today I was developing the assignment bot, but in sandbox mode I got a message that said: ‘‘Incorrect Bot ID’’ when I was in the Studio option
I gave it Configure, Reset Bot, and now the Sandbox mode option appears in gray.

The following appears on the screen:

If the welcome message is not configured, try setting the same and check the direct link.

Configure the fallback message in “home section” then issue will be resolved @Sagar

Am facing the same issue can you help me to solve the issue

Configure the Welcome message and fallback message in your bot and train it once. Then it will work properly.