Stopped working for me too, gutted as it was such a great way for converting to Mando TAB as well as whistles errr and occorinas (had to look that one up).

You can use Musescore to create TAB from the score it will also create a score from an imported ABC file and if you really dig into it you can alter the tuning of the strings.

Would love to see Mandolintab.net back up and running though.

P.