Sounds like you have application control turned on in Kerio but are not allowing applications to start, and you are not allowing internet connections, or even internal connections. Your printer will not work if you block internal connections.
Make sure Network Security > Trusted Area > Loopback is ticked as trusted.
Your internet connection should not be ticked as trusted.
In Intrusions, untick Enable Application behaviour blocking.
In Network Security > Applications, you should see rules like this:
If you see any 'deny' rules in any other columns, delete the rules unless you have set that rule for a reason. When that application again tries to connect out, allow it (as long as you trust the application of course.)
Make sure the rule for any other application is set to 'deny' for 'internet in'.
Go to Shields Up! and test you settings. Create a rule to permanently block any incoming connections.
https://www.grc.com/x/ne.dll?bh0bkyd2(You may need to allow incoming connections for messenger programs and online games or P2P networks: change the rule to internet/in to ask if you need programs like this to accept incoming connections.)