Check:

• Make sure your <form> tag has the enctype=”multipart/form-data” attribute
• Check php.ini for: file_uploads = On, post_max_size = 100M, upload_max_filesize = 100M (Note it’s “M”, not “MB”)
  You might need to use .htaccess or .user.ini if you are on shared hosting and don’t have access to php.ini.