in general, overlay traffic must match SD-WAN overlay rule.
you can attach the following outputs from both peers here if you prefer
fw monitor -F "<src>,0,<dst>,0,0" -F "<dst>,0,<src>,0,0"
example:
fw monitor -F "192.168.1.1,0,192.168.10.1,0,0" -F "192.168.10.1,0,192.168.1.1,0,0"
fw ctl zdebug + drop while greping client or server IP
for example:
fw ctl zdebug + drop | grep 192.168.10.1
#initiate the connection
check which tunnel chosen to carry the conn:
vpn tu conn <src> - <dst> - - (run that while the conn already opened)
copy the outputs.
you can also check on which SD-WAN rule the traffic matches if you don't see it in logs by:
fw ctl zdebug -m SDWANRB + all | grep PROB
#initiate the connection