Unable to load PDF template file in 1.4.6

This is the error I’m getting when I hit download Unable to load the requested file: invoice_templates/pdf/default.php
and it has permissions to this file.
I don’t understand why I’m getting this error.
I’m getting it on my fork and on stock 1.4.6

Log:

>  DEBUG - 2016-03-24 11:51:43 --> Config Class Initialized
>     DEBUG - 2016-03-24 11:51:43 --> Hooks Class Initialized
>     DEBUG - 2016-03-24 11:51:43 --> MY Utf8 Initialized - Hack for PHPUnit to run
>     DEBUG - 2016-03-24 11:51:43 --> UTF-8 Support Enabled
>     DEBUG - 2016-03-24 11:51:43 --> URI Class Initialized
>     DEBUG - 2016-03-24 11:51:43 --> Router Class Initialized
>     DEBUG - 2016-03-24 11:51:43 --> Output Class Initialized
>     DEBUG - 2016-03-24 11:51:43 --> Security Class Initialized
>     DEBUG - 2016-03-24 11:51:43 --> Input Class Initialized
>     DEBUG - 2016-03-24 11:51:43 --> XSS Filtering completed
>     DEBUG - 2016-03-24 11:51:43 --> Global POST and COOKIE data sanitized
>     DEBUG - 2016-03-24 11:51:43 --> Language Class Initialized
>     DEBUG - 2016-03-24 11:51:43 --> Language Class Initialized
>     DEBUG - 2016-03-24 11:51:43 --> Config Class Initialized
>     DEBUG - 2016-03-24 11:51:43 --> Loader Class Initialized
>     DEBUG - 2016-03-24 11:51:43 --> Controller Class Initialized
>     DEBUG - 2016-03-24 16:51:43 --> Invoices MX_Controller Initialized
>     DEBUG - 2016-03-24 16:51:43 --> Config file loaded: application/config/invoice_plane.php
>     DEBUG - 2016-03-24 16:51:43 --> Session Class Initialized
>     DEBUG - 2016-03-24 16:51:43 --> Helper loaded: string_helper
>     DEBUG - 2016-03-24 16:51:43 --> Session routines successfully run
>     DEBUG - 2016-03-24 16:51:43 --> Helper loaded: url_helper
>     DEBUG - 2016-03-24 16:51:43 --> Database Driver Class Initialized
>     DEBUG - 2016-03-24 16:51:43 --> Helper loaded: form_helper
>     DEBUG - 2016-03-24 16:51:43 --> Form Validation Class Initialized
>     DEBUG - 2016-03-24 16:51:43 --> Helper loaded: number_helper
>     DEBUG - 2016-03-24 16:51:43 --> Helper loaded: pager_helper
>     DEBUG - 2016-03-24 16:51:43 --> Helper loaded: invoice_helper
>     DEBUG - 2016-03-24 16:51:43 --> Helper loaded: date_helper
>     DEBUG - 2016-03-24 16:51:43 --> Helper loaded: redirect_helper
>     DEBUG - 2016-03-24 16:51:43 --> Model Class Initialized
>     DEBUG - 2016-03-24 16:51:43 --> File loaded: application/modules/settings/models/mdl_settings.php
>     DEBUG - 2016-03-24 16:51:43 --> Model Class Initialized
>     DEBUG - 2016-03-24 16:51:43 --> Language file loaded: language/english/ip_lang.php
>     DEBUG - 2016-03-24 16:51:43 --> Language file loaded: language/english/form_validation_lang.php
>     DEBUG - 2016-03-24 16:51:43 --> Language file loaded: language/english/custom_lang.php
>     DEBUG - 2016-03-24 16:51:43 --> Helper loaded: language_helper
>     DEBUG - 2016-03-24 16:51:43 --> File loaded: application/controllers/../modules/layout/controllers/layout.php
>     DEBUG - 2016-03-24 16:51:43 --> Layout MX_Controller Initialized
>     DEBUG - 2016-03-24 16:51:43 --> File loaded: application/modules/invoices/models/mdl_invoices.php
>     DEBUG - 2016-03-24 16:51:43 --> Model Class Initialized
>     DEBUG - 2016-03-24 16:51:43 --> Helper loaded: pdf_helper
>     DEBUG - 2016-03-24 16:51:43 --> File loaded: application/modules/invoices/models/mdl_items.php
>     DEBUG - 2016-03-24 16:51:43 --> Model Class Initialized
>     DEBUG - 2016-03-24 16:51:43 --> File loaded: application/modules/invoices/models/mdl_invoice_tax_rates.php
>     DEBUG - 2016-03-24 16:51:43 --> Model Class Initialized
>     DEBUG - 2016-03-24 16:51:43 --> File loaded: application/modules/payment_methods/models/mdl_payment_methods.php
>     DEBUG - 2016-03-24 16:51:43 --> Model Class Initialized
>     DEBUG - 2016-03-24 16:51:43 --> Helper loaded: country_helper
>     DEBUG - 2016-03-24 16:51:43 --> Helper loaded: template_helper

Could you please verify that this file really exist?
Because the core templates shipped with InvoicePlane were overhauled and renamed from default to InvoicePlane

So can I rename InvoicePlane.php to default.php?

No. Instead change your invoice and quote template settings.