I don't see the automatic update button on the admin home screen. Why not?
Run the command-line updater to get an error message explaining the problem.
A common cause is that your server cannot connect to our update server to download the update.
If you get a message that says "We could not fetch version information from our web server", you may need to open the SSL port (443) outbound to *.deskpro.com addresses.
In addition, check that the connection isn't being blocked by firewall/antivirus software, your SELinux configuration, etc.
If you're upgrading from a version before 410 on Linux and are getting SSL-related error messages, see this article.
You may find that manually updating to the latest version restores the update button.