Hemle Bracket Clock chime malfunction

Good day,

My Hemle bracket clock (1050 - 020) has 3 chimes (Westminster, St Michael & Whittington)and they all work if prompted which I do by moving the 'silent' lever up and down. (The 'silent' lever is to the side of the clock behind the clock face, on the left of the clock if you look at it from the back).

However, the clock does not chime automatically - it is supposed to chime on the quarter hour. The hour gong also works if prompted by juggling the 'silent' lever but will not gong automatically on the hour.

It appears that the mechanism is working alright, it just won't chime by itself. I was concerned that I may have over wound the spring, so I spent hours juggling the 'silent' lever and it chimed every time. This would suggest it has not been over wound.

Could there be a simple solution to this problem?
Many thanks.

Paul Richards