Try deleting the "manifest.jmf" file and "index.html" file from the target folder, then try uploading using jAlbum again. Any change? Also try changing "connection type" under Tools->Upload/Manage from "ftp (edtftpj)" to "ftp (ftp4j)" and retry the upload. Any change?
You could try checking your web root is still correct, see https://jalbum.net/help/en/jAlbum/Upload
If it doesn’t work you could supply more information, like suggested by setting the logging level to fine.
Hit the rightmost button in jAlbum's upload window to also reveal files (and not just folders). Now locate and delete that "manifest.jmf" file. Finally select the target album folder and reattempt the upload. Does it work now? Expect a longer initial delay as jAlbum compares the local and remote files before uploading again.