If you forgot the WiFi password you set for your Stratus 1S or Stratus 2S, you will need to perform a Stratus factory reset as described in the appropriate Stratus Pilot's Guide:
To return Stratus to its default factory settings, press and hold the power button for 30 seconds while the device is on.
Once the factory reset is complete, all of the LED indicators will cycle from green to yellow to green.
The factory reset will change the LED dimming and power mode settings back to default. The WiFi password will be turned OFF, but can be reactivated using ForeFlight Mobile.