Zotero cannot save PDFs

myshao

Zotero can only capture PDF files when the software is first launched. After a while, it can only capture entries and cannot save PDFs.
https://s3.amazonaws.com/zotero.org/images/forums/u8988850/5uc6227950fcxd65uatf.png
https://s3.amazonaws.com/zotero.org/images/forums/u8988850/oolqdfhss4lokdpxkcpb.png