I went to review my Pi-hole web interface and received a notice that web access to the interface was being blocked by Pi-hole. I have two instances on my network and they appear to be blocking just fine, I just cannot access the web interface. I am running
::: Pi-hole version is v2.12.1 (Latest version is v2.12.1)
::: Web-Admin version is v2.4 (Latest version is v2.4)
Which OS are you running, and what address are you using to access the admin page?
I am running on Raspbian GNU/Linux 8 (jessie) I am using an internal IP address.
Twenty characters. 
Yes, that's correct.
Typically if you see that page, its from a 404 error. Can you type here exactly what you are entering in the browser address bar so we can see if there are any issues? If you are using private addresses there's no need to redact them as no one can access your installation via private addresses. And I'm not understanding what "Twenty characters" means?
The forum requires a minimum of 20 characters. My original reply was "Yes, that's correct". I think I found the problem, it was a PEBKAC. I was neglecting to put /admin. Now I feel like an idiot. Sorry
It's a common issue, we're actually putting in a feature next release that will redirect the http://pi.hole address to http://pi.hole/admin/ for you in case you leave it off.
That would be great! Thank you for your prompt help, Dan.
I have the latest version. I installed it just last night and I am still getting pi hole blocking when I use the dns name I setup in the Local DNS area.
Use http://customdomainname/admin/ (the important part is /admin/ at the end.
Note this is a 3 year old thread you've replied to.
My comment of http://pi.hole still stands.
Ok it is old however i am still getting the same behavior. If i use the IP address I get the redirect page however if i use the DNS name I defined in Local DNS I get the blocking message. I am happy to start a new thread/issue
You're seeing the intended behavior.
http://customdomain.lan will 404. If you want the admin page you need to type http://customdomain.lan/admin/.
Only http://pi.hole will automatically redirect to http://pi.hole/admin/. You can not use a custom domain as a bare URL.