That was it: https://engineering.purdue.edu/hanquist/publications/theses

This works now so thanks for your help. For someone reason, I have a giant "url" symbol but that may be an issue on our side

Thanks, Christian. You are right, that was the entry.

After fixing that entry, I am able to see it correctly with this:
https://bibbase.org/show?bib=https://bibbase.org/zotero-group/khanquist/4882481&filter=type:thesis,keyword:group

But if I add this to my webpage, it does not filter by group:
https://engineering.purdue.edu/hanquist/publications/theses