edit for posterity, and I might be an idiot
While researching a similar post on this forum (https://retropie.org.uk/forum/topic/3287/noob-xbox-controler-question/8) I discovered that connecting the charging cable/mount to an xbox 360 wireless controller does not make it a "wired" controller; a truly wired controller cannot be used "wirelessly." In retrospect, this now seems painfully obvious...
AgentlemanNinja, I'm not sure exactly what your controller situation is, but if you are running a true wireless controller with the charging cable, like I was, that might explain your problem.
Hope this is helpful.