If the person that created the initial page access token is removed as an admin from the Facebook page your bot is linked to, the page access token will become invalidated, causing your bot to no longer be authorized to post messages to the page.
We advise you to test any changes to the developer apps and pages within Facebook within the testing environment first, before changing anything in the production environment.
If you are currently experiencing issues as described above, please follow the steps below to fix it:
In the Facebook Application on http://developers.facebook.com, go to Products > Messenger > Settings and scroll down to 'Token Generation'
Select the right Facebook page and copy the Page Access Token
On our platform, go to 'Settings'
Change the Page Access Token to the one you copied from Facebook and click the 'Push to bot' button.
If these steps do not fix the issue, please contact us through our support channels.