[Plugin: WP-UserOnline] CodeColorer conflict and permalink question

I use CodeColorer plugin. Then I go to https://www.mysitename.com/useronline, I get something like this
1 [page_useronline]

Any solution?

Second question. Is it possible to make something like https://www.mysitename.com/?useronline which shows a page with users online information using default theme’s template. I know plugins and themes can have such functionality, like Splix theme has php-generated css ?splix-css=css

Plugin: https://www.ads-software.com/extend/plugins/wp-useronline/
Plugin: https://www.ads-software.com/extend/plugins/codecolorer/