Hi! Are you getting these errors in Google Search Console or a 3rd party tool?
If it is a 3rd party tool, then it is possible that their crawler do not support SPAs.
This is related to how the collections are working in SiteJet, see here: Include the actual data from the collection item in the html markup
However, I guess the simple way to fix this is to add a redirect to your first blog-post (or an existing page).
Example:
Redirect yoursite_dot_com/article to yoursite_dot_com/article/your_first_article_slug