Revoked the API key you were using? Worry not, because you can simply create a new key and update the connection. Do NOT delete the exchange connection as doing that will stop importing new transactions.
To update a connection with new API key:
- Open the app and go to 'Settings'.
- Open 'Manage Exchange Connections' and open the connection you want to update.
- Enter the new API Key and Secret and tap 'Update connection'. Voila!