Customfield error - v1.5.3

Hi.

I still can’t make my custom fields works after upgrading to version 1.5, thanks in advance for any suggestion.

If I include the code to display custom field, I receive error below, and it is working fine if I remove this part therefore I am quite sure the custom fields are causing the problem.
A PHP Error was encountered
Severity: Notice
Message: Undefined index: User
Filename: pdf/InvoicePlane_FL.php
Line Number: 61

I have checked the reference page
https://wiki.invoiceplane.com/en/1.5/templates/customize-templates#custom-fields
and follow the guide to adjust the code, here is my current codes:

<?php echo $custom_fields['User']['ABN']; ?>

It is to display an ABN number as seen and I also have the settings in the system as:

I have also tried changing the orders however it doesn’t help.

Is there anything else I can try?

Thanks.

Spelling. It’s <?php echo $custom_fields['user']['ABN']; ?> (small u in user!)

Thanks - it works.
I thought I have to use upper case because I saw “User” in the table.