At 10.7.1, I have created this very simple model:
However, when I run the model, it immediately fails at the Add Field tool, with this response:
Executing (Add Field): AddField C:\WorkSpace\CDLT\PARCEL_MODEL\Parcels.shp cdlt_acres DOUBLE # 2 # # NULLABLE NON_REQUIRED #
Start Time: Tue Mar 3 16:09:08 2020
Adding cdlt_acres to C:\WorkSpace\CDLT\PARCEL_MODEL\Parcels.shp...
ERROR 999999: Error executing function.
Failed to execute (Add Field).
Unfortunately, there is no help for ERROR 999999, so I turn to SE for assistance. I've checked the shapefile's geometry, and restarted Arc, but the error still persists.
FWIW, here are the contents of the model's Add Field tool: