I have a TZ170 at work and have administrative priveledges and can't connect to my slingbox at home.  I didn's see any answers posted to your problem, but was wondering if it got solved eventually.

Do you have a Sonicwall at work?  I didn't try it at another location, but tech support at sling said they could see it from there.

I have set up a Slingbox Pro behind a TZ170 (Sonic OS Standard) with no problems.  In that case it is a double NAT situation and still works fine.  It is not clear from the original post if double NAT is being used or not.  If so, on the Action Tech make sure you port forward to the Sonicwall's WAN IP adress (not its LAN IP).  In a double NAT situation, the trick which BK missed is you have to set up an implicit port forwarding rule on the Sonicwall.  Unlike other firewalls, there is no explicit page to set up port forwarding rules.  To get through a Sonicwall NAT and using private IP address (the case here) you have to set up a Slingbox service and assign the Slingbox TCP port you use.  Then set up a rule that allows access from WAN to the specific Slingbox IP for that specific service.  That effectively create port forwarding on the TZ170.

On my TZ170 NAT is the only WAN option, so the above config applys, but if using Enhanced OS maybe there are other options. If you are not using NAT on the Sonicwall and it only has a LAN IP (true router mode) which is on the same subnet as the Slingbox, then I think you you need to port forward from the Action Tech to the Slingbox IP not the Sonicwall IP.