What is the ruling on completing the expiatory fast or restarting it entirely, in the event that the menstrual cycle prevented the completion of two consecutive months of fasting as atonement for masturbating during the daytime in Ramadan?

First, you must sincerely repent to Allah for this forbidden act. If your masturbation resulted in the emission of semen, then your fast is broken, and you are only required to make up that day's fast, without expiation. This is because expiation is only obligatory for breaking the fast through sexual intercourse, according to the majority of scholars. Your past fasts are considered supererogatory. If your masturbation did not result in the emission of semen, then there is nothing upon you.