Invoice emails URL now showing blank page

[Lindsay Webb 0]

Hi. We have a problem with email invoices created in WHMCS. These have been working fine for years but now it has failed & we don't know why so don't know how to start looking into a fix.
When an invoice is sent out it includes a link for the customer to click on which should take them to the log in page & on to their account/invoice (Cannot be sure as the link doesn't work!). The domain works https://my.iapuk.biz but the full URL does not.
Example:
https://my.iapuk.biz/index.php?m=invoicelogin&k=f95adb4d7a16f93916200fecb78c08bf459bc68c
The template code looks like this:
Dear {$client_name},

This is a notice that an invoice has been generated on {$invoice_date_created}.

Your payment method is: {$invoice_payment_method}

Invoice #{$invoice_num}
Amount Due: {$invoice_total}
Due Date: {$invoice_date_due}

Invoice Items

{$invoice_html_contents}
------------------------------------------------------

Payment will be taken automatically on {$invoice_date_due} from your credit card on record with us. To update or change the credit card details we hold for your account please login at {$auto_login_link_html} and click Pay Now then following the instructions on screen.

{$signature}

Any help would be greatly appreciated.

Extra Info:
We use Xero for accounting.
We use 20i for hosting & domain.
 

Anyone any ideas?

[pRieStaKos 38]

You should ask the developer that created the auto login…as it’s not a WHMCS feature.