You can find the link to a working *test* installer in that message.
Note: a test installer is only provided for PostgreSQL 11.5 – for other versions you need to use the zip archives from the download page and install the minor update by hand.
Best regards,
Wilm Hoyer.
I got the following error (see attached) when attempting installing all available versions, with the exception of 9.3.25 (Not Supported), which installed.