Reverting change as it does not help.

Module maintainer for the context_http_header has a spelling mismatch between the module machine name  and the project machine name that they have not fixed in over a years time. Run the following in drush to install from drupal.org

drush dl context_http_headers
drush en context_http_header

or  use my github fork of the project that changes themodule name to match the project name.