It sounds like you have multiple unrelated issues going on here– from USB cables to difficulty installing Inkscape. I would highly recommend that you try to solve one at a time. This can get frustrating quickly otherwise.
If you are getting messages that say “failed to connect to axidraw”, then something is wrong. That could be a USB cable, trying to connect to the AxiDraw too soon after starting up the Raspberry Pi (I suggest to give it a solid 15 second waiting period after booting for it to recognize USB devices), or something entirely different. If you aren’t sure whether an issue is due to the RPi or the AxiDraw, you might try connecting to your computer instead.
There are any number of different commands that can test whether the servo is moving — these include (yes) toggle, but you can also use the manual lift and lower commands, direct commands from the interactive python API, direct EBB commands, the setup tab in Inkscape, and plotting files.
If the servo motor is not raising and lowering but X and Y motion are working correctly, then the servo could be dead, but that can also result from having the pen-up and pen-down heights set the same or having the servo motor disconnected.
I’m not sure what the toggle issue has to do with installing Inkscape.
I have not had difficultly installing Inkscape on Raspberry Pi, but I definitely recommend against doing it– it’s a small computer with relatively few resources (speed and memory). If there is any way to do what you need to on the R Pi _without_ using Inkscape, I highly recommend that you do so.