Why does it say it could not decrypt?

Either the password is wrong or the file was changed or damaged after it was encrypted. The two cases cannot be told apart.

Are my files uploaded?

No. Files are read and processed inside your browser. They are never sent to a server, and closing the tab discards them.

JavaScript is turned off. InspireTools processes files in your browser, so the tools need JavaScript to run.

Open a file that was encrypted with the Encrypt File tool.