I had this problem and it took me a while to resolve it. When the 'hi clear' command is used in a nord theme function, it makes the Lualine's background disappear. After I found that, I made the lualine file be called only after nord.nvim had already run. For this reason, I think this warning is important, because there may be several people who will experience the same error.
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Just make sure to set the theme to "nord", as "nord" already
exist built in to lualine
+
+ If the lualine's background has become transparent, make sure that
+ lualine setup is being called after the nord theme has been applied.
vim:tw=78:ts=4:ft=help:norl: