Check your code carefully to ensure the right email address / merchant ID is being used.
Check your firewall settings aren't blocking the HTTP POST messages from Nochex.
Create a mail function that emails you soon as the code should have been called, that way you can see if the code is being called then you know that there is something in your code that needs changing.
Order details not coming through
If your order details have not come through and this only happens intermittently we have now added functionality that resets Callback to get the details sent through. Just follow the instructions below to reset Callback in turn sending the order details through:
Login to your Nochex account
At the control panel click Transaction History
Click on the symbol under the Callback column for a particular transaction to show a popup
You will see more information on the transaction and press the Reset Callback button
The status should turn from ongoing to passed when Callback has been resent, Note: this may take a couple of minutes
You should now get the order details showing for that transaction