It Just doesn't seem to work

[deHakkelaar]

You can test connectivity by doing below DNS lookup on a Windows, Linux or Mac client PC:

nslookup pi.hole <PIHOLE_IP_ADDRESS>

And you can test if a client is configured properly with below one if you leave out the "<PIHOLE_IP_ADDRESS>" bit.
Results should resemble above nslookup:

nslookup pi.hole

If they dont resemble, you configured something wrong somewhere:

How do I configure my devices to use Pi-hole as their DNS server?

Three methods Generally, there are three different methods that will enable devices on your network to be protected by Pi-hole. 1. Define Pi-hole's IP address as the only DNS entry in the router Rationale Only is italicized here for a reason: Pi-hole needs to be the only DNS server because it intercepts queries and decides whether or not they should be blocked. If you have other DNS servers configured, you may be sent to the correct domain, bypassing Pi-hole completely. Because of this, we re…

And if your router is lacking settings described in above FAQ:

How do I use Pi-hole's built in DHCP server (and why would I want to)?

Using Your Existing Router For Network-wide Ad Blocking You might not need to use Pi-hole's DHCP server: In many home environments, your router also functions as your DHCP server. In this case, you can often set Pi-hole to be the DNS server for your network clients in the router's DHCP (or LAN) settings page, which allows all of your network clients to block ads simply by connecting to the network. Setting it up this way is also what makes Pi-hole very powerful for network-wide ad blocking. W…

Below an example on one of my client PC's with 10.0.0.1 being my router and 10.0.0.2 being Pi-hole:

C:\>nslookup pi.hole 10.0.0.2
Server:  noads.dehakkelaar.nl
Address:  10.0.0.2

Name:    pi.hole
Address:  10.0.0.2

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C:\>nslookup pi.hole
Server:  noads.dehakkelaar.nl
Address:  10.0.0.2

Name:    pi.hole
Address:  10.0.0.2

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C:\>ipconfig /all

Ethernet adapter Local Area Connection:

   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
   IPv4 Address. . . . . . . . . . . : 10.0.0.11(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Lease Obtained. . . . . . . . . . : woensdag 21 maart 2018 16:45:05
   Lease Expires . . . . . . . . . . : donderdag 22 maart 2018 16:45:05
   Default Gateway . . . . . . . . . : 10.0.0.1
   DHCP Server . . . . . . . . . . . : 10.0.0.2
   DNS Servers . . . . . . . . . . . : 10.0.0.2