Hi Fidel, when L2L IPsec tunnels don't work, it usually is a problem with 1 of 3 things.
1. Crypto mechanics
2. Routing
3. NAT
You say the "VPN is up" so I'll take that to mean your crypto mechanics are good but please verify you have good phase 1 and 2 SA's established by the output of.
1. show crypto isakmp sa (or show crypto ikev1 sa)
2. show crypto ipsec sa
If both of those show established SA's then direct your attention to this part of the output of 'show crypto ipsec sa'.
example: #pkts encaps: 7260, #pkts encrypt: 7260, #pkts digest: 7260
#pkts decaps: 8698, #pkts decrypt: 8698, #pkts verify: 8698
This will tell you a lot about which side(s) has the issue. If you have zero encaps and zero decaps on both ASA's then likely you have some work to do on both ASA's. If you have 1 ASA that has some encaps incrementing and the other ASA has decaps incrementing, then focus your efforts on the ASA that has the decaps incrementing. It means that ASA is receiving IPsec encapsulated traffic but not sending anything back. (Almost ALWAYS a routing or NAT problem)
This is where you'll need to examine your NAT and routing to ensure they are correct.
Without posting your entire config and topology these are difficult to advise on.
What I've tried to do here is give you some direction on how to troubleshoot this on your own.
Also, make heavy use of the tool packet-tracer when troubleshooting VPN's, it can sometimes shed some light
