What size is the video? You may need to increase the downloadable file size.
For example, to increase the limit on uploaded files to 10 MB:
- Add the below to the relevant php.ini file (recommended, if you have access). Note that for some hosts this is a system-wide setting. However, for hosts running PHP as a CGI script with suexec (for example) you may be able to put these directives in a php.ini file in your Drupal root directory.
- upload_max_filesize = 10M
- post_max_size = 10M
- Add the below to your .htaccess file in your Drupal root directory.
- php_value upload_max_filesize 10M
- php_value post_max_size 10M
The PHP documentation states that the memory_limit setting also affects file uploading. Generally speaking, memory_limit should be larger than post_max_size. If this is an issue, see the page on how to Increase memory available to PHP