Hi guys, do you guys know what problem is in this command?

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[Hương Trà Trần]

grep -oP "\b([0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3})\b" /var/log/syslog | wc -l : this work

but this does not work:
*grep -i "Fail" /var/log/syslog | grep -oP "\b([0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3})\b"
*