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A few ideas...
rm -f /usr/local/nagios/var/nrpe.pid (code=killed, signal=KILL)
Check for syntax errors in /usr/local/nagios/etc/nrpe.cfg and files in the include directory.
See if nrpe is managed by xinetd. ls -l /etc/xinetd.d/nrpe
systemctl restart nrpe
How was nrpe installed?