If ping is not working over the SonicWall VPN, assuming you have enabled ping on the interface, allowed all the firewall exceptions, etc. Ping is probably not working because it’s being intercepted by SonicWall’s Intrusion Prevention Settings (IPS). By default, ping is listed as a Low priority intrusion. Untick the Low setting in IPS on each SonicWall device in the path of the ping (local and remote ends). You should now be able to ping across the VPN.
To enable ping across a VPN without disabling the Low IPS setting, set the category drop-down for ICMP in the IPS Policy and then click the pencil icon. You can then set the Prevention drop-down to Disable and then click OK.