Problem with IP Forwarding Virtual server

I recently created a new HA pair. One unit has been running for a year or so as a standalone. So I created a new unit then built the HA pair, synched the configuration and everything is happy. However, if I failover to the "new" unit in the HA pair no IP forwarding traffic seems to pass through the unit in either direction. I can't ping through or establish any connections from the nodes on the internal side - web servers. From the external side I can't ping BUT if I connect to the HTTP VIP it works. So I know I can establish a direct connection to the web server through the VIP. It just appears that the forwarding traffic doesn't work. I have verified that the web server/node is getting the arp entries after the failover so it knows where to send traffic.

A quick tcpdump from the web server shows the ICMP getting into the F5 but never getting a response.

If I fail back to the "original" unit then things work fine with no issues.

I can ssh to the "non-working" unit and can ping internal and external ip addresses, all my nodes, etc... So i know that network connectivity is good.

The configuration is pretty basic so I'm a bit lost on what could be happening.

Anyone have any ideas of something to check?

thanks