Phone/Customer support for free software that has no advertising built into it doesn't really exist in this world for the most part, if you've seen it anywhere else they are probably looking to build a customer base before they go behind a paywall.
HP, and Autodesk, offer free peer-support forums for you to seek out help: you found this one at Autodesk, and here is HP's https://h30434.www3.hp.com/t5/Printers/ct-p/InkJet
Now... Post a screenshot of your PLOT command pop-up, show us what you are doing, then explain if you are trying to plot from MODEL or PAPERSPACE.
HP, and Autodesk, offer free peer-support forums for you to seek out help: you found this one at Autodesk, and here is HP's https://h30434.www3.hp.com/t5/Printers/ct-p/InkJet
Now... Post a screenshot of your PLOT command pop-up, show us what you are doing, then explain if you are trying to plot from MODEL or PAPERSPACE.