Can't update to version 3.10.2 from Joomla! 3.9.3 Stable, error message says "error" on the joomla update page when downloading and installing the package.
If I remember correctly, there is a bug in Joomla 3.9.3 causes this error
So better, update your site to latest version of Joomla, then try again. If update still does not work, submit a support ticket sending us super admin account of your site so that we can check it for you