I recently installed WPMUDEV Q & A (question and answer) plugin but when tried accessing it through: http://domain.com/questions/ it showed me a 404 not found error.
My permalink structure was set to non-default but still i was getting a 404 page not found when trying to access questions and answers plugin by wpmudev from front end.
How to solve WPMUDEV questions and answers plugin giving 404 page not found error:
The solution to this issue is relatively simple.
Simply goto your wordpress settings > permalink and change permalink to any other structure that it is on currently and save it. Once you do so, immediately change it back to your previous structure and save again.
This will refresh the .htaccess rewrite rules for your permalinks and now the questions answers plugin will be accessible from the front end normally!