The cable you link to is stereo at both ends. The plug at the speaker end is the correct type but not wired for your application.
The 3.5mm jack of the PC is unbalanced stereo.
The 1/4" TRS jack on the speaker is balanced mono.
You need one of the these https://www.rdlnet.com/product.php?page=164
or you can make something similar
Simple Way to Convert Stereo to Mono: This is going to be a tutorial on how to take a stereo audio source from a phone for example and convert it to a mono signal to use with a mono amplifier or a two channel amplifier( I'll show you how to do this), and anything that needs a mono signa…