Why "no route to host", but VPN tunnel troubleshoot shows remote host?

[jmaxwellUSAF]

Hello.
On an ASA 1120 I'm troubleshooting a failing L2L VPN turn-on. The remote engineer requests I run a traceroute to his device. When I try this I experience error "no route to host."
This doesn't make sense to me because during troubleshoot it is true that packets are exchanged between devices (so a route definitely exists by definition). It is true that a few days have passed since the VPN endpoints communicated.
Also,

show route

reveals "Gateway of last resort is not set".
Route exists= "S 0.0.0.0 0.0.0.0 [255/0] via 172.16.1.1, inside tunneled"

How do I successfully run this requested traceroute?

Thank you.

[jmaxwellUSAF · Accepted solution]

THIS IS GREAT (below). Wow what a tool!...

#packet-tracer input [src_int] protocol src_addr src_port dest_addr dest_port [detailed] [xml]
#packet-tracer input inside(interface from which the interesting traffic is generated) icmp x.x.x.x( interesting traffic at your end ) 8 0 x.x.x.x(interesting traffic at remote end) detailed

Troubleshooting Access Problems Using Packet-Tracer - Cisco Community

[jmaxwellUSAF]

What is the meaning/relevance of  "8 0" in below code?

#packet-tracer input inside(interface from which the interesting traffic is generated) icmp x.x.x.x( interesting traffic at your end ) 8 0 x.x.x.x(interesting traffic at remote end) detailed

Thank you.

[MHM Cisco World]

8 0 meaning echo request