My DNS changes don't appear to be taking effect
There may be times where you map a domain and, although the settings are correct, the domain doesn't resolve to the site as expected. You probably need to wait for the DNS settings to propagate throughout the web as you may currently be getting a cached response over the network.
Can I check how things are resolving?
Yes. whatsmydns.net is a great tool for checking to how records are currently resolving around the world:
DNS Checker - DNS Propagation Check & DNS Lookup
Can I speed up the changes?
To a degree, although there are many layers to it. Generally, there will be a waiting period to factor in. Most of the time, DNS settings take effect within a few hours but it can take up to 48 hours according to various sources on the web.
You can try using Google's DNS cache flushing tool to try and speed things up a touch:
Flush Cache | Public DNS | Google Developers
You can try flushing your DNS cache on your machine: