Internal Server Error when trying to complete purchase

This site is still in demo mode. It’s a sort of craigslist for car adverts – the language is changeable in the upper left corner of the site.

When I try to complete purchases on the site, I can pay with credit card and it appears to check out all right, but after a few seconds the screen scrolls to the top, and the text “Internal Server Error” appears instead of the wanted confirmation of a successful purchase.

I have involved both the supplier of the theme and the hosting company. The supplier has tried to switch to a default theme and the problem remains. Therefore they deny that it can have anything to do with their theme. The hosting company says everything works fine on their end as well. Both of them points at WooCommerce as a possible source of the error.

I will say, that everything used to work fine until perhaps 1-2 months ago. I can’t say what triggered the negative change!

I get the following error codes in the WC status field:

2018-08-29T14:53:54+00:00 CRITICAL Uncaught Error: Call to a member function set_price() on null in /var/www/klassikermarkedet.dk/public_html/wp-content/plugins/subscriptio/includes/classes/libraries/rightpress-wc-legacy.class.php:1045
Stack trace:
#0 /var/www/klassikermarkedet.dk/public_html/wp-content/plugins/subscriptio/includes/classes/libraries/rightpress-wc-legacy.class.php(46): RightPress_WC_Legacy_9::product_set_price(NULL, '500')
#1 /var/www/klassikermarkedet.dk/public_html/wp-content/plugins/subscriptio/includes/classes/subscriptio-order-handler.class.php(170): RightPress_WC_Legacy::__callStatic('product_set_pri...', Array)
#2 /var/www/klassikermarkedet.dk/public_html/wp-content/plugins/subscriptio/includes/classes/subscriptio-order-handler.class.php(83): Subscriptio_Order_Handler->new_order()
#3 /var/www/klassikermarkedet.dk/public_html/wp-includes/class-wp-hook.php(288): Subscriptio_Order_Handler->woocommerce_create_order(NULL)
#4 /var/www/klassikermarkedet.dk/public_html/wp-includes/plugin.php(203): WP_Hook->apply_filters(NULL, Ar

I hope somebody can help out.

BTW: I’m not very technical, so all reply’s should be written in clear language, please 😉

Regards,
Rune

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