Hello Stephen,
Thanks very much for the interest in the sample set.
Are you referring to the downloads listed here on the Milan Digital Audio website: https://milandigitalaudio.com/1741-bovenkerk-hinsz/ ?
If so, that page mentions that they were for Hauptwerk v3/v4, so they wouldn't work anyway in Hauptwerk v5+ and v3/v4 are no longer supported, so maybe that page just hasn't been updated yet. (I'll let Brett know that it may need updating.)
For Hauptwerk v5+ you can instead download the full sample set here:
viewtopic.php?f=10&t=17988
Before installing it, send a message to Francois at support [at] hauptwerk.com , letting him know your iLok account name (not the password) and requesting a trial licence for the sample set. Once you've activated the trial licence you can then install and use the sample set in full for seven days.