I've tried to install this mod (which I think is great!) and I also added the checkout steps add-on. I get to enter in my information and then receive this error:

Warning: main(includes/templates/template_default/templates/tpl_checkout_default.php): failed to open stream: No such file or directory in /home/content/(userroot)/html/includes/templates/serious_docs/common/tpl_main_page.php on line 119

Warning: main(includes/templates/template_default/templates/tpl_checkout_default.php): failed to open stream: No such file or directory in /home/content/(userroot)/html/includes/templates/serious_docs/common/tpl_main_page.php on line 119

Fatal error: main(): Failed opening required 'includes/templates/template_default/templates/tpl_checkout_default.php' (include_path='.:/usr/local/lib/php') in /home/content/(userroot)/includes/templates/serious_docs/common/tpl_main_page.php on line 119

I've tried removing it, and then reinstalling it, but I get the same error.

What did I do wrong? lol

Thanks!