Better late than never. Just go back to pray ASAP and also tell ZSNN the reason why you were late and apologize also.
But most importantly if you make any promise when praying to ZSNN, please do fulfill it.
Don't give up ladies! We too pray and took the egg and I remembered it took some time before getting pregnant also. I pray to both ZSNN at TPY and also went to Bugis Guan Ying Temple to pray for both my pregnancy. So don't be hishearted! Jiayou!