Problem

After installing a Magento 2 module, this error occurs in the checkout:


main.CRITICAL: Broken reference: No element found with ID 'checkout.header.wrapper'


Cause

The module was not installed properly. This is not a bug in the module.


Solution

Please follow the installation instructions for Composer from this article, section "Magento 2".


Also make sure to follow the instructions from the module's readme file, and execute all steps exactly as shown there.