ipFrom a name to an address
DNS is a distributed system for finding records associated with domain names. A browser may resolve address records before connecting to a site. One name can point to several addresses, so a domain does not always have a one-to-one relationship with a permanent IP.
What changing DNS changes
Using a different DNS resolver changes the service you ask for records. It does not by itself change the public IP assigned by your ISP. VPN applications can change both DNS and the traffic exit, which is one reason the two operations are sometimes confused.
Separate resolution from connection
Investigate DNS when a name cannot be resolved, and routing or service access when an address is found but the connection fails. Typing an IP into a browser is not an equivalent HTTPS test because certificates and virtual hosting matter. Do not classify the fault using that result alone.
The name resolves but the site fails
Receiving an address answer means at least that DNS lookup completed. The subsequent HTTPS connection, certificate, or server response may fail instead. Replacing the hostname with an IP can select a different virtual host. Record whether the error concerns resolution, connection, or certificates rather than changing DNS for every failure.
Further reading
DNS concepts — RFC 1034 ↗Put it into practice
Inspect one public IP, or compare a list of addresses with the bulk lookup tool. Location results are approximate.
Single lookup ↗ Bulk lookup ↗