Hi Mary, welcome to the board.
Do you have multiple machines? Is it possible you are trying to use the foot from a different machine?
There is nothing electronic about this, just simple plug-and-go, so not a lot of troubleshooting we can do other than what it sounds like you've already done. Is the plug directional, meaning it will only go in one way? Maybe have someone else in your house try it; sometimes I don't realize where I'm going wrong until I ask my husband or one of my sons to try whatever I'm having an issue with.