What could be causing the issue with Opera browser not being able to connect to Google Drive and OneDrive, preventing attachments from being added to Google Calendar and folders from being uploaded to Google Drive and OneDrive? The issue has persisted since at least January and occurs on both Windows 10 and 11, while Firefox and Chrome are not affected.

Also there is a direct solution that you can use to upload your files/folders from your computer to Googledrive/Onedrive , just try a third party tool like Gs Richcopy 360 or Syncback , search both