I am experienced installing CMS software, so I understand about the requirements and connecting to the database and all that. I am installing Omeka as a subdirectory in which Joomla is installed (mentioning that since I saw that some people with WordPress had problems). I have uploaded all the files. The php version is 5.6.29. The .htaccess file is uploaded. I have set up a database with user having "all privileges." I have edited the db.ini file on the server replacing the XXXXes with the appropriate "localhost" and database name, user, and password. the Files folder and its subfolders all have 755 permissions.
When I browse to the directory, I get a 404 file not found message.
Thanks for any assistance.