Pagination doesn’t work

Today I bought the Q & A plugin and it works fine. It works simple. However, I can not solve a problem. Several questions have been asked, but there is no clear solution.
If I click on page 2 or next, he comes to the general category view, but not to the next page of questions. I have already disabled permalinks and yoast plugin, but nothing helps.
What am I doing wrong? It\’s about site:

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