
If she is dound not to be in whelp it is worth having a premate test doen now to determine if she ovulated this season (the test should indicate if she ahs ovualted in the last couple of months.
The most common reason for bitches to miss is incorrect timing, have you mated on the same days each time?
Have you used the smae male both times? A freidn used a dog twice and the bitch missed, did premate next time and still tried same dog and ended up with a litter of 10. She did only one premate the previous season and the bitch missed,. it is important to get several tests done.
Start before the bitch is likely to ovulate (around day 8 for many), so that you start with a negative reading and then test every other day until it shows levels rising, then test daily until it indicates ovulation.
Remenber that a bitch produces immature eggs at ovualtion and they won't be ready for fertilization for another two days,a dn then the eggs shoudl stay viable for another two days or so.