If you are on MacOS 26.0+ and attempting to install a config, but you get the error "Profile installation failed: the 'MCX Settings' payload could not be installed. One or more keys in the payload must be installed in a device profile, not a user profile," here is how to proceed.
This error will be triggered if you are on MacOS 26.0 and have de-selected the option `Allow Mac Guest Account` in the config editor. Apple now enforces that this restriction is applied to the entire device, not just the signed in user.
To resolve this, you'll need to upgrade to a device-level profile that applies the restrictions to the entire Mac computer. See this help doc for instructions: