recoding a range of numeric values

Good that this worked for this example. I doubt that you get this error message because of the file's origin (or the labels). If this variable really exists in your data frame, I guess it must be your second idea: the way you are referring to the variable.

To be able to help you answer your question, I would need a minimal reproducible example. "The goal of a reprex is to package your code, and information about your problem so that others can run it and feel your pain. Then, hopefully, folks can more easily provide a solution." (FAQ: What's a reproducible example (reprex) and how do I do one?)