I noticed a lot of people having issues with the controllers lately, a lot of people can't fix it and have no clue what's going on, even using the calibration doesn't work, i was having the same issue tonight, i couldn't config any of the keys for my Snes gamepad, people are using different types and still having issues, i have one where it's a classic controlle with the classic end with the USB adapter, i just got it back from my bro after ages... and it worked fine before when i played on ZSnes, most people are using ZSnes but it's happening on Snesx9 too though, that one doesn't work for me though, i get that Dll error but ZSnes always does.
About 2 hours later of going through devices what not i finally decided to look in the obvious place... and that's Options in ZSnes, i looked at what's there and i honestly don't know what GFX Engines are so i unticked both of them, and low 'n' behold my controller was working and i could cofig the keys
,so if anyone if having issues i suggest going into the Options and untick stuff, the GFX Engines in ZSnes seems to be conflicting with it and stops it recognizing me pressing the buttons on my controller.