In case the Channel Manager is reporting errors like "Unfortunately, this is no longer available." or "Forbidden" while executing updates or requests towards Airbnb, then this may indicate that the connection between your Airbnb account and e4jConnect has been revoked. Hence, no longer valid.
The best thing to do in these cases is to restore the connection between your Airbnb account and e4jConnect. You can do this directly from your Airbnb account, by visiting the page "Account" and then "Privacy & sharing" where you will see the currently connected e4jConnect "App" as illustrated below:
Click on "Remove access" to disconnect your account from the e4jConnect Channel Manager, so that you can start again a new connection by clicking the button "Connect with Airbnb" from the page Settings in Vik Channel Manager.