You have more than one citation program installed on your computer (EndNote, Mendeley)
Your computer is not recognizing what program to open reference files (.ris, .nbib, etc.) with
Uninstall any citation management program you are NOT using (EndNote, Mendeley). Ensure Zotero is the only citation manager on your computer.
Right-click a reference file (.ris, .nbib, etc.) in your Downloads folder on your computer and select "Open with...", then navigate to Zotero (under Applications folder for Macs and Program Files for PCs). Ensure to select the option for ALL .ris and .nbib files.
You may also manually import each reference file (.ris, .nbib. etc.) by following these instructions for importing references.
Ensure Zotero is open in another window. It will not work if it's closed
Select the "refresh" button.
If the above options don't help, try saving your work and closing out of your paper and coming back into it.
Ensure Zotero is open in another window. It will not work if it's closed
Select the "refresh" button.
If the above options don't help, try saving your work and closing out of your paper and coming back into it.
Open the .Data folder.
For “Save as type:”, choose “XML” and save the XML file in the .Data folder
If you only want to export a subset of your library, check the “Export Selected References” box. Otherwise, make sure it is unchecked.
For more information, visit the Zotero documentation topic on exporting your library from EndNote.
For guidance on exporting files from Mendeley, visit the Zotero documentation topic on importing a Mendeley library into Zotero.