Before you start · Start Your Server

You need to be the server owner. The builder can reshape your whole server, so only the owner sees it. Moderators and managers can't open it.
The bot needs to be in your server. It needs at least View Channels to read your current layout, and Manage Channels plus Manage Roles to build.
A few things stay off limits without Administrator. Channels that are hidden from everyone and roles that sit above the bot can't be changed. Those steps of a build fail with a clear note about why, and you can unlock them by moving the bot's role higher or granting it access to those channels.
Check the "building as" badge. The design page shows a small building as @bot badge naming the bot that makes every change. If your server runs its own custom bot, that bot is the one that needs the permissions, not the shared YourBot.