The bot menu disappears and appears by itself.

The bot was created and worked, but one day the menu disappeared - the bot does not respond to commands.

You forgot to CHANGE THE TOKEN in @BotFather, or you are intentionally using an old Key!
This causes a conflict between your old bot and the new one created using @MenuBuilderBot.

When migrating to @MenuBuilderBot from other constructors, make sure to delete all old bots (before creating a new bot with the old key), but the best practice of all is NOT TO USE your old bot's Token (Key). Register a New Bot Address in @BotFather or Change the Key of the old Address. After receiving the New Token, use it for your new bot on @MenuBuilderBot platform.

Solution:
1. Go to @BotFather
2. Find your bot
3. Click change Key and copy the new one
4. Go to @MenuBuilderBot - Manage Bots
5. Find your bot
6. Press Update Token
7. Send new token