Any other antivirus or firewall apps that might be blocking? (Unlikely if the Sandbox vault works.)
Also if this wasn’t suggested yet, in Obsidian open the developer tools and console. Check if you see any errors when exporting.
And here are some additional threads to read, and check if they are applicable. These might be completely irrelevant to you, but I am including them just in case:
Do you have the note (or any note) open in Acrobat Reader, or another PDF reader? Export to PDF silently fails if PDF is open in Acrobat Reader
Is your vault, your main HD, or your write location on a network share? This might be relevant if you are testing in Google Drive, but I don’t know if that is a “network share”. Obsidian fails to render .pdf when accessing a vault via windows network share