Trying other mirrors.
To address this issue please refer to the below knowledge base article 

https://access.redhat.com/articles/1320623

If above article doesn't help to resolve this issue please create a bug on https://bugs.centos.org/



 One of the configured repositories failed (onlyoffice repo),
 and yum doesn't have enough cached data to continue. At this point the only
 safe thing yum can do is fail. There are a few ways to work "fix" this:

     1. Contact the upstream for the repository and get them to fix the problem.

     2. Reconfigure the baseurl/etc. for the repository, to point to a working
        upstream. This is most often useful if you are using a newer
        distribution release than is supported by the repository (and the
        packages for the previous distribution release still work).

     3. Run the command with the repository temporarily disabled
            yum --disablerepo=onlyoffice ...

     4. Disable the repository permanently, so yum won't use it by default. Yum
        will then just ignore the repository until you permanently enable it
        again or use --enablerepo for temporary usage:

            yum-config-manager --disable onlyoffice
        or
            subscription-manager repos --disable=onlyoffice

     5. Configure the failing repository to be skipped, if it is unavailable.
        Note that yum will try to contact the repo. when it runs most commands,
        so will have to try and fail each time (and thus. yum will be be much
        slower). If it is a very temporary problem though, this is often a nice
        compromise:

            yum-config-manager --save --setopt=onlyoffice.skip_if_unavailable=true

failure: repodata/repomd.xml from onlyoffice: [Errno 256] No more mirrors to try.
http://download.onlyoffice.com/repo/centos/noarch/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not Found

Reason: there is a problem with the yum source address. Either check the yum source or replace it with a new one.

The following is Baidu’s search result (error): Yum source file has a problem, not index cache. Clear cache is useless; So the way down here is a little bit big. Either view the yum source file, or change it to the yum source file on a normal machine</ mark>

This error is caused by a problem with the yum repository and can be solved by using the following two commands.
`yum clean all` # Clear the index cache of all yum commands
`rpm --rebuilddb` # The command to rebuild the RPM database

Solution 1: find the error report: http://download.onlyoffice.com/repo/centos/noarch/ Repair or delete the yum source file
solution 2: copy a Yum source from another normal Yum machine
verification method: Yum makecache verify whether the yum index cache can be generated normally, and remember to clear all the index caches first Yum clean all to verify