I had a similar issue a little while ago, which I asked about here. You may want to check that out and provide a little more info, eg:
- Wired or Wireless
- Gamepad Make and Model (I’m assuming standard Microsoft Xbox 360 USB?)
- OS, IDE, MonoGame version
I hope you can find out why it isn’t working. Mine kind of just fixed itself, I still don’t know what caused the issue.