When installed AJAX register I get the following.
* It was not possible to copy the selected file.
* JInstaller::install: Failed to copy file: /var/www/vhosts/pilotjourney.com/httpdocs/pjtmp/install_49ea62c95e67a/site/language/en-GB.com_ajaxregister.ini to /var/www/vhosts/pilotjourney.com/httpdocs/language/en-GB/en-GB.com_ajaxregister.ini
* It was not possible to copy the selected file.
* JInstaller::install: Failed to copy file: /var/www/vhosts/pilotjourney.com/httpdocs/pjtmp/install_49ea62c95e67a/admin/language/en-GB.com_ajaxregister.ini to /var/www/vhosts/pilotjourney.com/httpdocs/administrator/language/en-GB/en-GB.com_ajaxregister.ini
As a result some of the images and messages do not display correctly