Perhaps this is a known issue. You can't put a codeblock directly after a list, even separated with line breaks. It came up in this question, where I finally just added a colon between the list and codeblock so that it would look right.
Here's a list:
- First line
Second line
This should be a code block, check the markdown!
(there needs to be at least one normal character in this line, or the next codeblock won't render either. Line breaks don't do it)
This is also a codeblock
Edit:
I see that this has been discussed on meta.stackexchange.com; here and here are two examples. I don't see anything indicating that this behaviour will change.
But there are some good workarounds in those answers. My preference is to use
<b></b>
or a blank html comment
<!-- -->
as a separator.
---
on it in Markdown) right before a code block, as a separator. \$\endgroup\$ – Dave Tweed Mar 2 '17 at 17:19