[Koha] Fines always zero

[Chris Brown]

Hello,

I am a relative newcomer to Koha.

My system (Koha 17.05 on Debian) is not calculating fines (they are always
zero). I have checked:

1. There is a non-zero fine set in my default circulation rule (the only
rule at the moment)
2. The cron jobs seem to be running ... e.g. I see a backup file created at
06.25 each morning.
3. I have also tried running /etc/cron.daily/koha-common manually but the
fines are still zero.

Any suggestions on the likely cause, or how to investigate further?

Thanks!

Chris Brown