Issue the command: yum clean all
This happens because yum didn't get the new packages list from the repo server. Usually it's preceded by a message
Yum Error: "Not using downloaded repomd.xml because it is older than what we have"
Cleaning yum cache will force it to redownload the packages list, and consequently, recognize the packages.
If this doesn't help, you could also try cleaning some cache in rm /var/cache/yum/.....