Registering .day domain – Error: "Extended attribute: day_agree is required"

[xNASHx]

I’m encountering an error when trying to register a .day domain through WHMCS (v8.5.1) using eNom as the registrar.

Error: Extended attribute: day_agree is required.

This seems similar to a previously reported issue with .app domains:
https://whmcs.community/topic/304253-unable-to-register-app-domain/

What I’ve Done:

I created a custom domain field for .day by cloning the .bio format from dist.additionalfields.php, and added it to:

/resources/domains/additionalfields.php

Here is the entry I used:
 

// .DAY
$additionaldomainfields['.day'][] = [
    'Name' => '.DAY SSL Agreement',
    'LangVar' => 'day_agree',
    'Type' => 'tickbox',
    'Description' => '<sup style="cursor:help; text-align:justify;" title=".app is a more secure domain,'
        . ' meaning that HTTPS is required for all .app websites. You can buy your .app domain name now,'
        . ' but in order for it to work properly in browsers you must first configure HTTPS/SSL to serve'
        . ' the domain. I, the Registrant, understand and agree to the .app Registration Policy."
        >Learn More</sup>',
    'Required' => true,
];

The checkbox appears as expected in the admin UI and client area.
 

Module Debug Log:

POST sent to eNom(sensitive data changed):

id=*************&pw=**************************************&tld=day&sld=mydomain&numyears=1&IgnoreNSFail=Yes&EmailNotify=1&NS1=ns1.example.com&NS2=ns2.example.com&NS3=&NS4=&NS5=&RegistrantFirstName=John&RegistrantLastName=Doe&RegistrantOrganizationName=ExampleOrg&RegistrantJobTitle=Director&RegistrantAddress1=123+Example+St&RegistrantAddress2=&RegistrantCity=ExampleCity&RegistrantStateProvince=EX&RegistrantPostalCode=12345&RegistrantCountry=US&RegistrantEmailAddress=john.doe%40example.com&RegistrantPhone=%2B1.5555555555&RegistrantStateProvinceChoice=S&AdminFirstName=John&AdminLastName=Doe&AdminOrganizationName=ExampleOrg&AdminJobTitle=Director&AdminAddress1=123+Example+St&AdminAddress2=&AdminCity=ExampleCity&AdminStateProvince=EX&AdminPostalCode=12345&AdminCountry=US&AdminEmailAddress=john.doe%40example.com&AdminPhone=%2B1.5555555555&TechFirstName=John&TechLastName=Doe&TechOrganizationName=ExampleOrg&TechJobTitle=Director&TechAddress1=123+Example+St&TechAddress2=&TechCity=ExampleCity&TechStateProvince=EX&TechPostalCode=12345&TechCountry=US&TechEmailAddress=john.doe%40example.com&TechPhone=%2B1.5555555555&AuxBillingFirstName=John&AuxBillingLastName=Doe&AuxBillingOrganizationName=ExampleOrg&AuxBillingJobTitle=Director&AuxBillingAddress1=123+Example+St&AuxBillingAddress2=&AuxBillingCity=ExampleCity&AuxBillingStateProvince=EX&AuxBillingPostalCode=12345&AuxBillingCountry=US&AuxBillingEmailAddress=john.doe%40example.com&AuxBillingPhone=%2B1.5555555555&command=purchase&Engine=WHMCS8.5&

Response from eNom(sensitive data changed):

;URL Interface
;Machine is xxxxxxxxx
;Encoding Type is utf-8
Command=PURCHASE
APIType=API
Language=eng
ErrCount=1
Err1=Extended attribute: day_agree is required.
ResponseCount=1
ResponseNumber1=xxxxx
ResponseString1=Validation error; missing; extended attribute
MinPeriod=1
MaxPeriod=10
Server=xxxxx
Site=
IsLockable=True
IsRealTimeTLD=True
TimeDifference=+06.00
ExecTime=0.000
Done=true
TrackingKey=xxxxxxxxxx
RequestDateTime=4/14/2025 2:32:56 PM

Issue:

Even though the custom field is visible and required, WHMCS is not including the day_agree attribute in the API request to eNom.

Question:

Is there anything additional I need to do to ensure WHMCS includes this custom field in the API call for .day domains? Has anyone resolved this with .day, .app, or other Google-managed TLDs?

Thanks in advance for your help.

WHMCS Version: 8.5.1
Registrar Module: eNom
PHP Version:  7.4.33