I'm not sure which ping feature you're referring to, as there are several. If you're referring to the online status indicator documented
here: this pings the computer name, not the IP address. Changing the IP address manually will have no effect on the online status indicator. If the status indicator is saying the machine is offline when it isn't, there is either a DNS issue (computer name pointing to the wrong IP address) or the machine is firewalled.
Hitting Rescan on the asset page triggers a connection to the computer name (not the IP address) as well by the way. Most scanning methods connect to the computer name, the exception being IP Address Range Scanning. If DNS is pointing to an incorrect IP, scanning with name based scanning methods will cause the computer's "main" IP to be incorrectly identified and the scan to fail. You can see which scanning methods scanned a machine and when in the computer's Scan Time tab.