If you selected ‘use my device location’ during the sign-up process for Fluttr, your location will auto-change to reflect wherever you are at that moment. 

To disable/override auto-location, and instead set and save a specific location, navigate to the Search screen, tap ‘Filters’, and tap the pin icon in the top right of the Filters screen. This brings you to the ‘Set location + radius’ screen. Make your new adjustments and tap ‘Save.’ You can also disable location sharing via your device’s local settings.