Hello. The user is in Nigeria. On his Android phone, he opens our sites without problems ( https://main-site-git-main-zetradex-team.vercel.app/ as an example), but on his MacBook, our sites do not open. The site simply does not respond. The problem is definitely not in the application itself, since I uploaded the same application to Netliffey and everything opens without problems. How can I solve this problem? I thought that the problem might be in the user’s MacBook, but the user also checked the availability of the site on his friend’s iPhone and the site also did not open.
The domain troubleshooting guide can help with most custom domain configuration issues. You might be able to use that guide to solve it before a human is available to help you. Then you can come back here and share the answer for bonus points.
You can also use v0 to narrow down the possibilities.
There are known issues with some ISPs in Nigeria blocking some IP addresses. If your DNS provider allows CNAME flattening for your apex domain, then using cname.vercel-dns.com. for that may help.
This thread has more tips:
Please give those ideas a try and let me know if you still have trouble with this 
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Hello. Sorry for the long reply. Adding CNAME really solved the problem, but one of our resources started having accessibility bugs and we returned everything to A records. Now we are trying to gradually remove A records from all our sites and transfer them to CNAME. I will write here about the result, I hope that within a week we will be able to solve this problem
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Hey @pavelzetradex. Did you get it working?