I don't understand your problem. It seems you are describing several different problems.

Can you post the exact URL that gives you Requested Blog does not exist! ?

That would be this URL >> http://alexliebrecht.com/blogs/2016/10/31/b2evolution-6-7-8-erschienen-mit-bugfixes

Logged out of the blog everything works well, but logged in as admin the comment area is not displayed and this error, which I addressed above.

OK, so, as I am logged out, I still don't see a problem. Please post a screenshot of your complete screen when you are logged in.

The screenshot can be found in the appendix of this forum posts.

Interesting. Never seen that before. Can you create a test account for me so I can log in and look at the URLs involved more closely? Thanks.

OK, first, can you please try with a default Bootstrap skin and then any other skin you download from the skins repository please?

Does that make a difference?

Then, please configure a debug password and send it to us so we can see a debug log of your system.

Hi,
It actually worked. I now set the skin "Bootstrap Blog" and so does it. The comment function under the blog post is displayed.

So it really was the other skin.

I have to look now, if there is an update for the first skin and this I can then install. Let's see if it works.

What is the name of the skin that doesn't work?

thanks.

It is the skin at http://skins.b2evolution.net/flat-skin

I had used this once and now I look again in the Bevo skins more precisely. I find something more suitable.