Spamassassin connect to spamd on ::1 failed - doesn't scan messages

Hello,

I have:
Centos 7.2.11
Plesk 12.0.8
postfix-2.10.1-6.el7.x86_64
spamassassin-3.4.0-2.el7.x86_64

I detect some messages aren't scanned by spam, I just receive

<code>
May 16 10:40:36 plesk135 spamc[8789]: connect to spamd on ::1 failed, retrying (#1 of 3): Connection refused
May 16 10:40:36 plesk135 spamd[2005]: spamd: connection from localhost [127.0.0.1]:35592 to port 783, fd 5
May 16 10:40:36 plesk135 spamd[2005]: spamd: using default config for...

Spamassassin connect to spamd on ::1 failed - doesn't scan messages