OK,, this just got really confusing then.
If it's all hooked as shown it should be working.
https://xdevs.com/doc/HP_Agilent_Key...0Operating.pdf
page 11
Given that all cables are OK.
Perhaps the marker is set up in an odd way, Pentode may be able to help there, it's clear that the oscilloscope and the 8601A Generator/Sweeper seem to be set correctly.