It’s a browser security issue, not an OpenRPA issue.
They will not allow javascript to trigger an upload, so you need to set “virtual” to false on the element click, that is used to click the upload button.
On certain browser versions, this will BLOCK the browser, so the extension will stop working while the “select file to upload” dialog is open. If that is the case for you, you will need to use a separate workflow to handle the file upload dialog. There is several posts on the forum about that, you can search for.