Manual URE plugin update scenario without losing any data:
1) Deactivate plugin
2) Delete old files under plugin folder using FTP
3) Copy new files into plugin folder
4) Activate plugin back
In case your site missed URE license key somehow, starting from version 4.18.5 I removed the feature, when URE license key was deleted automatically in case of site domain, absolute path or database name change. Additionally you may specify URE license key at wp-config.php as the PHP constant. Look at version 4.18.5 changelog.
