If you get this message for BOT Inboxer in Facebook app dashboard "Your Webhooks subscription callback URL has not been accepting updates", there may several reason for that.
Most cases, if your server goes down for any reason like maintenance or other, Facebook can't get any response from callback URL. In this time Facebook send this notification. If it continues for long time, Facebook may stop sending webhook callback anymore until further action taken from you.
To know more about webhook response time read here.
In this case, first check if your server is up & running.
Check your BOT, If it is working or not. If it is working then fine, don't need to do anything, just avoid the notification.
If not working, Just try by Disable BOT & Re-Start BOT , then see if bot is working or not.
If BOT still not working …
first go to Your APP dashboard.
From Left side, go Webhook menu.
Click on Edit Subscription. Put the Callback URL & Verify Token taken from BOT Inboxer APP settings menu, then click on Verify & Save.
Next go to Messenger->Settings menu. Go webhook section, edit event & click on save.
Next go to BOT settings in the system, in bot settings click on Disable BOT & Re-Start Bot again.
Now check the bot, it should work fine.
How to check webhook error log
To check the error during webhook call that Facebook got, go to APP's Messenger Tabs -> Settings , Then scroll down and go Webhook section , The click on Show Recent Errors
There may be also other reason on server level issue. Example it may happen that your server's firewall has blocked the Facebook's IP from where webhook call is coming or other DNS issue or any Proxy issue of your server. In this case, contact your hosting provider.
However beside these you should follow some best practises .
1. Don't keep EZ Inboxer & XeroChat in same domain. (If you have BOTH Software)
2. Don't install multiple copy of XeroChat or EZ Inboxer in same domain.
3. Avoid enabling same page for BOT from both XeroChat or EZ Inboxer or in both copy.
4. Check if you have any other unused Facebook APP which has the same settings for webhook
And after re-enable of the webhook it may happen that after a few minutes it get disabled again by Facebook. It may happen actually when there are a lot server error happened in last 3 days. In this case Facebook disable the webhook due to error rate in last couple of days. Facebook nowhere notify the actual error threshold. But this error log is generally cleared in 3 days. So in this case, you may need to wait for 72 hours to clear error log & re-enable the webhook.