Internal Server Error at checkout

Hi,

We are having a problem on the checkout stage. We are getting Internal Server Error notification and payment isn’t proceeded. We tried to deactivate different plugins so that it could solve the issue but it didn’t work. On the source page there is a warning of mixed content, but does it really cause the problem?

Are there any other possible causes and how to solve this issue?

Looking for your response,

Best regards,
Ekaterina

https://wordpress.org/plugins/woocommerce/