DNS resolution failing for common domains

Subdomains for both domains mentioned by you frequently appear on blocklists, and are currently found on Steven Black's hosts as well.

If you still want to access those subdomains, you must allow them via an entry in Pi-hole's Whitelist.

In general, you can find out if and in which lists a domain occurs via Tools | Query Lists.

In addition, it may be worth taking a further look at