I am supporting a customer who has a IPSEC Site-Site VPN set up between a SA520 and SR520. The tunnel is up, live, and active. However, I can only seem to initiate connections from the SR520 LAN to that of the SA520. For example, I can ping devices in the SA520 LAN and make RDP connections in the SA520 LAN from the SR520 LAN but not from the other direction. I expect the problem in in the SA520 but I can't figure it out. Everything "looks" right. Firmware version of the SA520 is 2.1.71.
I have this problem too.