while I'm REALLY new to pfsense (like 4 days old haha), I had a problem similar over my ipsec vpn. I could ping from the remote office to the main office, but not the other way around.
I ended up going to Firewall -> Rules -> IPsec @ the remote office, and made an "any" rule (any protocol, source, port, destination, gateway). Once I did that, I could ping and traceroute both ways across the link.
Basically, you have to treat the IPsec tunnel as any other network adapter it seems. Hope this helps.