Helpe to rebuild my blog entry content type link

I'm guessing the reason is likely because of the machine name of the content type. When you change the name of a content type, the machine name isn't automatically changed with it. This means that your old link would be the working link to add to it while this new link won't work because the machine name hasn't been changed. If you just go to "node/add", try to click the "Blog" content type from there to see if you can add it. To get the link "node/add/blog" to work, you have to change the content type's machine name by going to "admin/structure/types" and then clicking "edit" next to the content type and then next to the name field there should be something that says "machine name" with an edit link next to that. Click the link and change the name to "blog". Save your changes and the new link should work.

Also, for future reference, we can't exactly see the error message with your site for this kind of thing when we don't have accounts/admin access. For such things, you should take screenshots and post/link them or copy/paste the error messages directly.