Vancouver brackets style
I changed the Vancouver style (with superscript numbers) to Vancouver brackets, but the old cites stayed formatted as superscript. Adding a new cite, it cite it in brackets. How do you automatically change the cites to brackets?
Upgrade Storage
If so, make sure they are active citation. If not something is going on with your document. See https://www.zotero.org/support/kb/existing_citations_not_detected