Depend on your version,you can check the status of VPN tunnel from SmartDashboard.
Depend on our firewall policy, did you allow ping? Did you log the stealth rule? (Maybe it got drop in stealth rule and did not log).
Did traceroute show correct route from one end to the other over the tunnel? Or it did not even reach the peer device?
VPN issue can be caused by many different reasons. My recommendation wold be to open a support ticket and have someone perform the troubleshooting steps with you to eliminate each possible cause.