Blank page when click PayNow button

I am using IP 1.5.9. Every feature worked fine except it shows blank page when click PayNow button.

I saw this Blank page in payment page but don’t know how to solved this.

No error logs in PHP, Apache, Chrome Web Developer tools.

Testing invoice: https://invoice.d2thanh.com/guest/view/invoice/CAzXMcgw0bRG2HkWF8nOPi7pJ5tKajhV

My .htaccess:

## Run InvoicePlane in a subfolder
## If you are using a subfolder please remove the hash in front of the line ‘#RewriteBase /subfolder’
## and replace ‘subfolder’ with the actual name of your folder, i.e. ‘RewriteBase /invoices’

<IfModule mod_rewrite.c>

  RewriteEngine On
  #RewriteBase /
  RewriteRule ^index\.php$ - [L]
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteRule . /index.php [L]
  
  ## Remove the hash in front of the following two lines if you want to force HTTPS
  RewriteCond %{HTTPS} off
  RewriteRule ^(.*)$ https://%{HTTP_HOST}/$1 [R=301,L]
  
</IfModule>

Debug Logs when visit Guest URL and click on PayNow button:

DEBUG - 2018-05-18 10:29:29 --> UTF-8 Support Enabled
DEBUG - 2018-05-18 10:29:29 --> Global POST, GET and COOKIE data sanitized
DEBUG - 2018-05-18 10:29:29 --> View MX_Controller Initialized
DEBUG - 2018-05-18 10:29:29 --> Config file loaded: /home/d2thanh/invoice/application/config/invoice_plane.php
DEBUG - 2018-05-18 10:29:29 --> Encryption: Auto-configured driver 'openssl'.
DEBUG - 2018-05-18 10:29:29 --> File loaded: /home/d2thanh/invoice/application/modules/settings/models/Mdl_settings.php
DEBUG - 2018-05-18 10:29:29 --> File loaded: /home/d2thanh/invoice/application/modules/settings/models/Mdl_versions.php
DEBUG - 2018-05-18 10:29:29 --> File loaded: /home/d2thanh/invoice/application/controllers/../modules/layout/controllers/Layout.php
DEBUG - 2018-05-18 10:29:29 --> Layout MX_Controller Initialized
DEBUG - 2018-05-18 10:29:29 --> File loaded: /home/d2thanh/invoice/application/modules/invoices/models/Mdl_invoices.php
DEBUG - 2018-05-18 10:29:29 --> File loaded: /home/d2thanh/invoice/application/modules/invoices/models/Mdl_items.php
DEBUG - 2018-05-18 10:29:29 --> File loaded: /home/d2thanh/invoice/application/modules/invoices/models/Mdl_invoice_tax_rates.php
DEBUG - 2018-05-18 10:29:29 --> File loaded: /home/d2thanh/invoice/application/modules/payment_methods/models/Mdl_payment_methods.php
DEBUG - 2018-05-18 10:29:29 --> File loaded: /home/d2thanh/invoice/application/modules/custom_fields/models/Mdl_custom_fields.php
DEBUG - 2018-05-18 10:29:29 --> File loaded: /home/d2thanh/invoice/application/modules/custom_fields/models/Mdl_invoice_custom.php
DEBUG - 2018-05-18 10:29:29 --> File loaded: /home/d2thanh/invoice/application/modules/custom_values/models/Mdl_custom_values.php
DEBUG - 2018-05-18 10:29:29 --> File loaded: /home/d2thanh/invoice/application/modules/custom_fields/models/Mdl_client_custom.php
DEBUG - 2018-05-18 10:29:29 --> File loaded: /home/d2thanh/invoice/application/modules/custom_fields/models/Mdl_user_custom.php
DEBUG - 2018-05-18 10:29:29 --> File loaded: /home/d2thanh/invoice/application/views/invoice_templates/public/default-payment.php
DEBUG - 2018-05-18 10:29:29 --> Total execution time: 0.0662
DEBUG - 2018-05-18 10:29:58 --> UTF-8 Support Enabled
DEBUG - 2018-05-18 10:29:58 --> Global POST, GET and COOKIE data sanitized
DEBUG - 2018-05-18 10:29:58 --> Payment_Handler MX_Controller Initialized
DEBUG - 2018-05-18 10:29:58 --> Config file loaded: /home/d2thanh/invoice/application/config/invoice_plane.php
DEBUG - 2018-05-18 10:29:58 --> Encryption: Auto-configured driver 'openssl'.
DEBUG - 2018-05-18 10:29:58 --> File loaded: /home/d2thanh/invoice/application/modules/settings/models/Mdl_settings.php
DEBUG - 2018-05-18 10:29:58 --> File loaded: /home/d2thanh/invoice/application/modules/settings/models/Mdl_versions.php
DEBUG - 2018-05-18 10:29:58 --> File loaded: /home/d2thanh/invoice/application/controllers/../modules/layout/controllers/Layout.php
DEBUG - 2018-05-18 10:29:58 --> Layout MX_Controller Initialized
DEBUG - 2018-05-18 10:29:58 --> File loaded: /home/d2thanh/invoice/application/modules/invoices/models/Mdl_invoices.php
DEBUG - 2018-05-18 10:29:58 --> Total execution time: 0.0583

Thank you so much.

Need more information here.

Which payment provider do you use? Did test mode make a difference?

I used both PayPal Pro and PayPal Express in Test Mode too, but nothing different.