Hi Xia
As stated by Alix, the place of the footer tpl file changed. Are you working on the correct file? The location is: src/UI/templates/default/MainControls/tpl.footer.html. Which makes it:
Customizing/global/skin/myskin/UI/MainControls/tpl.footer.html
if you want to customize it in your skin. See: https://github.com/ILIAS-eLearning/ILIAS/tree/release_7/templates
As stated by Alix, the place of the footer tpl file changed. Are you working on the correct file? The location is: src/UI/templates/default/MainControls/tpl.footer.html. Which makes it:
Customizing/global/skin/myskin/UI/MainControls/tpl.footer.html
if you want to customize it in your skin. See: https://github.com/ILIAS-eLearning/ILIAS/tree/release_7/templates