If you can ping the Private interface of the 3015 from behind the 3002 then your tunnel is up and you have a routing problem, in that your network behind the 3015 doesn't know how to get to the network behind the 3002.
You need to add a route onto your network behind the 3015, that defines the network behind the 3002 and points to the Private IP address of the 3015. Then redistribute that route throughout your network if necessary.
Also make sure that your 3015 has a static route on it for the network behind the 3002 pointing to the default gateway of the 3015 out the Public interface (although the fact you cna ping the Private interface of the 3015 means you do have this, or you just have a default gateway defined and no more specific route which is also fine).