Add the following lines to the .htaccess file:
AddType application/vnd.ms-word.document.macroEnabled.12 .docm AddType application/vnd.openxmlformats-officedocument.wordprocessingml.document docx AddType application/vnd.openxmlformats-officedocument.wordprocessingml.template dotx AddType application/vnd.ms-powerpoint.template.macroEnabled.12 potm AddType application/vnd.openxmlformats-officedocument.presentationml.template potx AddType application/vnd.ms-powerpoint.addin.macroEnabled.12 ppam AddType application/vnd.ms-powerpoint.slideshow.macroEnabled.12 ppsm AddType application/vnd.openxmlformats-officedocument.presentationml.slideshow ppsx AddType application/vnd.ms-powerpoint.presentation.macroEnabled.12 pptm AddType application/vnd.openxmlformats-officedocument.presentationml.presentation pptx AddType application/vnd.ms-excel.addin.macroEnabled.12 xlam AddType application/vnd.ms-excel.sheet.binary.macroEnabled.12 xlsb AddType application/vnd.ms-excel.sheet.macroEnabled.12 xlsm AddType application/vnd.openxmlformats-officedocument.spreadsheetml.sheet xlsx AddType application/vnd.ms-excel.template.macroEnabled.12 xltm AddType application/vnd.openxmlformats-officedocument.spreadsheetml.template xltx
