Water enters bowl but ball does not move . . .

I just picked up a cable replacement kit (34106) for my Thetford toilet.
When the foot pedal is down water comes into the bowl but the waste ball does not move. I knew the seal needed to be replaced but now I wonder should I replace that old ball also. If you have experience with this issue and solved the problem please advice. Thanks in advance.

p.s. It is a Thetford style plus model.