Lookup failed

My Zotero worked for me yesterday. However, when I added the items by DOI (e.g., https://doi.org/10.1016/j.tra.2014.02.007) as usual, Zotero is not functional regardless of the doi format. It pops up this error "Zotero could not find a record for the specified identifier. Please verify the identifier and try again". Thank you very much for any suggestions.
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