Problem with opening sites deployed on vercel in nigeria

Hello. current configuration on dns provider:
@ A record 76.76.21.21
web A record 76.76.21.21 and several more A records for different resources
CNAME record is set for my and my.example.com resource works fine.

we tried to add one more record for @, in the end it turned out like this
@ A record 76.76.21.21
@ CNAME cname.vercel-dns.com

but after that the site became unavailable. we also tried to delete @ A record 76.76.21.21 and leave only
@ CNAME cname.vercel-dns.com the site was also unavailable. the problem could not be solved