The Stryd platform automatically calculates your Critical Power based on the last 3 months worth of your running data. If there is an issue with your auto-calculated CP, you can reset the calculation so that only runs from that point forward are being considered. You will get a new CP number after a few runs and the platform will again collect 3 months' worth of data.
You can currently only reset the Critical Power calculation with the Stryd app on the phone.
In the iOS and Android app, you can reset your CP under Settings > Debug Options > Reset Critical Power. See screenshot below: