Unable to register authentication agent: GDBus.Error

service dovecot restart
Redirecting to /bin/systemctl restart dovecot.service

** (pkttyagent:4531): WARNING **: 09:45:25.536: Unable to register authentication agent: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: Cannot determine user of subject
Error registering authentication agent: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: Cannot determine user of subject (polkit-error-quark, 0)
[ 09:45:26 root@janoko /var/log]$

Solution :

mount proc -o remount,hidepid=2 && mount proc -o remount,hidepid=0 && systemctl restart polkit.service