Editing module shows module XML data not available

From Joomla! Documentation

Other languages:
Deutsch • ‎English • ‎Nederlands • ‎español • ‎français • ‎русский

Some modules installed in Joomla 3.4 and higher (that previously worked in Joomla 3.3.6) show an error when attempting to edit

Errors reported[edit]

"Module XML data not available" when going to edit module (with no fields appearing)

Versions affected[edit]

Info non-talk.png
General Information

This pertains only to Joomla! version(s):- 3.4 and higher

What is the cause[edit]

Modules that have capital letters in their elements are now forced to lowercase during module installs (as a result of some standardisation in the installer). This results in case sensitive systems with the XML file being unable to be found.

How to fix[edit]

Ensure the module element e.g.

<filename module="mod_articles_category">mod_articles_category.php</filename>

has no capital letters in (as well as the appropriate XML file).