As CWP6/7 cannot be deinstalled you need to reinstall the whole OS. My advice is to run the installer again.
cd /usr/local/src
sh cwp-el7-latest
Let it finish and check again for pma. If it`s not working try like this:
cd /usr/local/cwpsrv/var/services
wget -q http://dl1.centos-webpanel.com/files/mysql/phpMyAdmin-4.6.6-all-languages.zip
unzip -o phpMyAdmin-4.6.6-all-languages.zip
mv phpMyAdmin-4.6.6-all-languages pma
rm -Rf phpMyAdmin-4.6.6-all-languages.zip pma/setup
mv /usr/local/cwpsrv/var/services/pma/config.sample.inc.php /usr/local/cwpsrv/var/services/pma/config.inc.php
ran_password=$(</dev/urandom tr -dc A-Za-z0-9 | head -c32)
sed -i "s|\['blowfish_secret'\] = ''|\['blowfish_secret'\] = '${ran_password}'|" /usr/local/cwpsrv/var/services/pma/config.inc.php
Please report if one of the ways is working.