I followed this Youtube tutorial https://www.youtube.com/watch?v=8f13lfnEKY8
and I believe it is the same as your setup.
#1 Pfsense running 2 openvpn server instances (has corresponding network as remote network)
#2 Pfsense running 1 openvpn client to Pfsense #1 (has both other networks as remote network)
#3 Pfsense running 1 openvpn client to Pfsense #1 (has both other networks as remote network)
I wasn't able to ping from the Pfsense #2 to #3 nor vice versa.
Both #2 and #3 were able to ping to #1
But then I noticed it was only the Pfsense itself.
Clients on Pfsense #3 could reach clients on Pfsense #2.
Clients could also ping all pfsenses....
Client pfsenses can't ping clients on other network.
In fact this is the main purpose of the site-to-site-to-site VPN, so I have it working now.
I now have a few questions:
Is this behaviour to be expected?
What do I need to do so #2 and #3 themselves can ping each other?
Should I consider this a bug?
Is this a recommended setup? I have a feeling it isn't as #2 and #3 can't reach each other anymore if #1 is failing.
Do I solve that single point of failure by creating a server instance on either #2 or #3, and let the other client connect to it??