I'm trying to calculate which CA zip codes border each other using Polygon Neighbors. I keep getting the error that the "Geometry is not M-aware". Initially, the dataset did not have M-values. I added them using "Feature Class to Shapefile" and turning on M-values in the Environment options. I also repaired the Geometry. I tried running Polygon Neighbors with disabled M-values in the Environment options. Same error every time. I don't know what else to do.
The dataset to which I added M-values is attached. FYI, I'm using ArcGIS 10.4