Check if your raspberry pi has internet access by SSH or Logging into it and see if you have enabled the right interface WIFI/ Ethernet to connect to internet and cross check the ip of LAN/ Ethernet.
Additionally check your router's additional settings for DNS Server Setting , i had it it misconfigured by adding Pi Hole Ip.
That is odd. There should be at least a line or two, as there should always be at least one client (localhost). Check that the quote symbol didn't get smartened - manually overwrite the quotes from your terminal.
Could you manually verify if the devices (client) ip settings. There could be some time cache / DNS Set to Router's IP address. Try to reset that as well just in case, hope your client does not have DNS like 184.108.40.206 (Google' DNS)
Also in the worst case, some times the router may have limited capabilities and have hardcoded DNS, try with a temporary router without internet connection should also do inorder to test the possibility. This was a pain for me initially to setup being a NOOB but once i completed it , i reaped the benefits of completing the setup.
Check you interface listing behaviour, its not set to "Listen only interface eth0" . I hope you have connected your raspberry pi to the router via lan cable, if so please choose "Listen only interface eth0" and connect with a lan cable. I am not sure how well pi hole will work as a DHCP over wifi - even i am facing issues making pi work over wifi. With land and "Listen only interface eth0" it should work for you.
Also try to ping google.com or any other public dns to verify ping response after changing settings, if that does not work you may modify resolv.config temporarily to add a name sever to verify everything. Please do restart the services and settings and pi boot once done