Error

ExecuteScalar requires an open and available connection

Cause

This error can appear if the project data hasn't saved properly.

Solution

1. Update both machines first. Confirm you're on the latest NVivo version on both the Mac and the Windows PC.
   1. Mac: NVivo → Check for Updates
   2. Windows: File → Product Info → Check for Software Updates
2. Move the file locally before converting. Copy the Mac project to the Desktop or Downloads folder on the PC and try converting from there — converting directly from a network drive, cloud folder, or external drive is a common trigger.
3. Resave the Mac project file before converting. 

• Open the file on the Mac. 
• Create a code, then save the file via File>Save.
• Delete that code, then save again via File>Save. Then click File>Close to close the file.
• Transfer the file to Windows and try to convert/open it.

If that doesn't resolve it:

1. With the project closed, go to File → Compact Project.
2. Open a new blank project on the Mac and import the original project into it.
3. Try the conversion again from this rebuilt copy.

One extra tip: when sharing the Mac file, compress it into a .zip first — uploading uncompressed via email, network shares, or cloud drives is a common cause of the corruption in the first place.