it is important never to blow on the reed,breath particles can cause rust.
Ralph is spot on,use a piece of paper,slip it between the reed and the reed shoe,I often find beard hairs are the problem.
when unscrewing the concertina,it is a good ideato put the screws carefully on the table, marked as to which hole they came from .
sorry, I was late arriving,HAQPPY NEW YEAR Deb C.