Routing between 2 networks connected via stub network not working as expected

        I am trying to work my way through an issue I am having with connecting 2 networks (datacentres) together via a private link. I have configured a stub network at both ends and this seems to work as expected, I can ping the remote end by both the stub IP and the switch IP, this shows me the link is up. What I can also do, is ping the default gateway on the remote side from the switch. What I cannot do, is ping anything else.

On the remote switch, I have the following routes defined; and on the remote gateway; What I am able to do; Ping 172.31.255.2 from switch1/site1 ping 192.168.210.5 (switch2/site2) from switch1/site1 ping 192.168.210.1 (asa2/site2) from switch1/site1

ICMP echo request from 172.31.255.1 to 192.168.210.1 ID=608 seq=2 len=0 ICMP echo reply from 192.168.210.1 to 172.31.255.1 ID=608 seq=2 len=0

ping 172.31.255.1 (switch1/site1) from asa2/site2 ping 192.168.210.5 (switch2/site2) from asa2/site2 What I can't do; ping 192.168.210.6 (a device/site2) from switch1/site1. It does not appear to be hitting the ASA. When I ping 192.168.210.1 from switch1/site1, I can see this in the icmp debug ICMP echo request from 172.31.255.1 to 192.168.210.1 ID=608 seq=2 len=0 ICMP echo reply from 192.168.210.1 to 172.31.255.1 ID=608 seq=2 len=0 I do not get anything in the icmp debug when I try to ping 192.168.210.7 which to me means it's not going to the default gateway and staying on the switch? Ultimately, I am trying to connect both sites up, but working my way through issues as I go and this is the first. Any suggestions?