returned 4XX status code - problem with tags

Hi everybody,

I am struggling to figure out the problem with 4XX status code. I did not have it before, but now I have 41 pages with this problem, it looks like this::

I think it has started when I added new tags. Unfortunately, I do not know how to fix it, I spent a few hours trying to make it work, but the problem is still there. Could you tell me how can I fix it?

Hi Jeremi

Try to flush your permalinks and then check again, this might be a permalink problem