You were part of a large club. Numerous community members have brought this issue to the attention of Fitbit and community advocates. Promises have been made that the developers are working to resolve this issue. No one can say whether it will just be that it will not reset step streaks or whether it will go back to the actual start date.
I hope now that Google has attached its name to Fitbit that issues raised by the community such as step streak will be addressed quickly into the satisfaction of all involved. On October 10, 2020 I started my step streak. Since then hit it has been reset twice. Tomorrow I will have to completed two years on my step streak. It is frustrating not being able to see step straight days that reflect the actual number. Tomorrow the Fitbit will show that I have completed a 20 day step streak.
