Site saying "This site can't be reached" for some users in some countries

My sites are

I can access both pretty well from the UK, but users in countries like Nigeria have reported issues with site loading through the site domain.

When I ask them to use netlify’s domain, it works. So I know it’s DNS issue.

The custom domains for both are

Could you help check if there’s an issue with how I setup DNS?

The DNS looks correct to me.