XF 2.0 any new buttons added in navbar do not change his background as button selected

Can you elaborate with some specific reproduction steps? If these are node navigation entries, then you'd need to update the selected node in the node configuration itself. For other cases there's not necessarily an expectation that any arbitrary navigation entry will appear as selected once you click on it. The routing system needs to be told which navigation entry should be selected in these cases, though it can usually be overridden fairly easily.
 
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