If you have not received a biphasic mark (little checkmark above ovulation day symbol), it could mean that Ava Fertility has not gathered enough data about your cycle yet to assess a biphasic parameter pattern, or that the pattern is not explicit enough.
Ava Fertility is only searching for a biphasic parameter pattern in the current cycle - retrospective assessments of past cycles cannot be done. 
Changing the period days of a past cycle can have a big impact on the assessment of the biphasic pattern. Since the assessment is not repeated, the app removes the confirmation checkmark. For this reason, as well as for maximizing Ava Fertility’s accuracy, don’t forget to enter the first day of your period correctly in each cycle.