The default maximum number of hops is 35. You can change this by manually editing your PingPlotter.ini file and adding this value to the [Advanced] section:
MaxHops=50
(or some appropriate number higher than 35, but less than 250).
Your PingPlotter.ini file is usually in the PingPlotter install directory (example: C:\Program Files\PingPlotter Pro). In some cases, it is in the Application Data directory (C:\Documents and Settings\(your profile name)\Application Data\PingPlotter\). This depends on your operating system.