Only some DOI registration agencies support content negotiation, which is what Zotero uses to retrieve metadata. In this case, a content-negotiation request to doi.org redirects to data.chinadoi.cn (which is ISTIC, I believe?), which refuses the connection.
Yes, it is ISTIC (=Institute of Scientific and Technical Information of China), see also http://api.crossref.org/works/10.11999/JEIT160915/agency . Besides content negotation any other API could help as well, e.g. for Airiti we use a different approach (e.g. 10.6220/joq.2012.19(1).01 for a test case). If there is any API for ISTIC then let us know and we can try to integrate it in Zotero.
10.6220/joq.2012.19(1).01
for a test case). If there is any API for ISTIC then let us know and we can try to integrate it in Zotero.