Hooks aren't up to date.
https://github.com/Parabot/Parabot-317-API-Minified-OS-Scape/blob/master/src/main/java/org/parabot/osscape/Loader.java#L44
Also that's the reason behind this error since the Client class name has changed, one way to fix this is reading the value out of the xml(hook file).
This has been discussed in our slack previously you can join in by contacting @Lord via PM.