Pointing your domains to a gh-pages branch requires three steps.
-
Add the Github IPs as
Arecords on Namecheap.
185.199.108.153
185.199.109.153
185.199.110.153
185.199.111.153 -
Add your Github domain as the
CNAMEalias on Namecheap.your_username.github.io.(mind the extra period!) -
Add a
CNAMEwith your new domain name in your repository. lowercase and nothing else

This is not correct anymore. Instead of
192.30.252.153and192.30.252.154, the IPs should be185.199.108.153,185.199.109.153,185.199.110.153and185.199.111.153.