It seems like while URL structure is set to /index.php?qa=123&qa_1=why-do-birds-sing, the example page url has the structure:
http://demo.question2answer.org/example-plugin-page
while I would expect something like:
http://demo.question2answer.org/index.php?qa=example-plugin-page
Below some screenshots made on demo.question2answer.org to make it more clear:
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask here, in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.