You do not have a menu item pointing to the list all Akeeba Ticket System categories for the English (United Kingdom) language. Ticket links may be broken until you add such a menu item.
#2 – 404 Error after installation
I guess you installed an .htaccess file from the SEF page of the component.
If you can access the administrator, go to
and in the top right you can find a "delete .htaccess" or "restore" functions that will solve this.
Otherwise, if you cannot access any part of your Joomla installation, you need to login with ftp or ssh and delete a file named ".htaccess" in the webroot of your website (i.e. where the configuration.php is). If you can't see it, most likely your ftp client will have an option to show hidden files which needs to be activated first.
If this fails, please open a private ticket with login details (either ftp or ssh) and I will fix it for you.