Hi there! 
I have a mirror (https://mirrors.upr.edu) that serve CentOS and others repositories like EPEL, UBUNTU and REMI. While doing updates to my servers I notices that none of my servers are using my CentOS mirror, but for EPEL and REMI repositories’ works fine.

# yum clean all; yum update
Loaded plugins: fastestmirror
Cleaning repos: base epel extras mariadb remi-php74 remi-safe updates
Cleaning up list of fastest mirrors
Other repos take up 11 M of disk space (use --verbose for details)
Loaded plugins: fastestmirror
Determining fastest mirrors
epel/x86_64/metalink                                                                   |  15 kB  00:00:00     
 * base: mirror.centos.iad1.serverforge.org
 * epel: mirrors.upr.edu
 * extras: centos.mirrors.tds.net
 * remi-php74: mirrors.upr.edu
 * remi-safe: mirrors.upr.edu
 * updates: ftp.usf.edu

I check if is out of sync in https://mirror-status.centos.org/#pr but is looks OK. I check the logs file web and I notice very low activity to CentOS repository. I also try some «curl» test on my servers, and I never get my server:

Normal Curl
# curl 'http://mirrorlist.centos.org/?repo=os&arch=x86_64&release=7'
http://mirror.centos.iad1.serverforge.org/7.9.2009/os/x86_64/
http://mirror.grid.uchicago.edu/pub/linux/centos/7.9.2009/os/x86_64/
http://mirror.cybersecurity.nmt.edu/centos/7.9.2009/os/x86_64/
http://mirrors.seas.harvard.edu/centos/7.9.2009/os/x86_64/
http://repos.eggycrew.com/centos/7.9.2009/os/x86_64/
http://ftp.ussg.iu.edu/linux/centos/7.9.2009/os/x86_64/
http://mirror.vtti.vt.edu/centos/7.9.2009/os/x86_64/
http://mirrors.cat.pdx.edu/centos/7.9.2009/os/x86_64/
http://mirrors.mit.edu/centos/7.9.2009/os/x86_64/
http://repo1.dal.innoscale.net/centos/7.9.2009/os/x86_64/


Forcing PR
# curl 'http://mirrorlist.centos.org/?repo=os&arch=x86_64&release=7&cc=pr'
http://mirror.centos.iad1.serverforge.org/7.9.2009/os/x86_64/
http://mirror.grid.uchicago.edu/pub/linux/centos/7.9.2009/os/x86_64/
http://mirror.cybersecurity.nmt.edu/centos/7.9.2009/os/x86_64/
http://mirrors.seas.harvard.edu/centos/7.9.2009/os/x86_64/
http://repos.eggycrew.com/centos/7.9.2009/os/x86_64/
http://ftp.ussg.iu.edu/linux/centos/7.9.2009/os/x86_64/
http://mirror.vtti.vt.edu/centos/7.9.2009/os/x86_64/
http://mirrors.cat.pdx.edu/centos/7.9.2009/os/x86_64/
http://mirrors.mit.edu/centos/7.9.2009/os/x86_64/
http://repo1.dal.innoscale.net/centos/7.9.2009/os/x86_64/


Testing other country (EC):
# curl 'http://mirrorlist.centos.org/?repo=os&arch=x86_64&release=7&cc=ec'
http://mirror.uta.edu.ec/centos/7.9.2009/os/x86_64/
http://mirror.epn.edu.ec/centos/7.9.2009/os/x86_64/
http://mirror.cedia.org.ec/centos/7.9.2009/os/x86_64/
http://mirror.ueb.edu.ec/centos/7.9.2009/os/x86_64/
http://centos.brisanet.com.br/7.9.2009/os/x86_64/
http://centos.mirror.letscloud.io/7.9.2009/os/x86_64/
http://mirror.facom.ufms.br/centos/7.9.2009/os/x86_64/
http://mirror.ci.ifes.edu.br/centos/7.9.2009/os/x86_64/
http://mirror.ufam.edu.br/centos/7.9.2009/os/x86_64/
http://centos.ufes.br/7.9.2009/os/x86_64/

There's something that I'm missing? Any Idea?

Regards.
Sergio E. López