Though the site says 6.18 is available, the download I get is 6.15.
John
Hello.
If you just install the latest version over an existing one it may not install properly.
It is essential to follow the instructions in the RTF document included in the install image.
The instructions detail removal of the old components which, if not done, will stop the update from installing.
Please get in touch if this does not resolve the issue.