Is the domainname set to the domain name of your IPA domain? I usually set CentOS/RHEL
servers hostname as the FQDN and when you install the free-ipa-client it sets the domain
name of the server to the freeipa domain name.
The next thing to check is if your hosts file is setup properly. Meaning the entry for
your host should be "IP FQDN alias". I have found if FQDN is not the first
entry, as it should always be, it can cause issues with sudo.
Did you add anything to the sssd.conf? SSSD usually works pretty good. This article may
help also. Let me know the outcome.