In my experience younger males lock for short periods and therfore you maynot catch it.

73 is pretty low so that should be enough to get breeding going and maybe why your male is probably not eating.

Also if the female is not cycling she maynot be interested at all in breeding and the male also maynot be as interested.

I will bet next year the male will be a much more aggressive breeder and lock for longer periods.

I have had males breed and produce babies their first year without ever seeing them lock only to watch them lock for days the next year.