Cannot insert the value NULL into column 'article_id'.table'distribution.dbo.MSrepl_commands'; the column does not allow NULLLS. INSERT fails. The subscription does not exist. The subscription could not be found. (Microsoft SQL Server, Error 515)
Solution: Dont back and restore database on Second node without creating Publicatiion on first Node,
Normally you should back up after creating the publication on the first node.
It solved my issue.