In ArcGIS Online, when running the Find Nearest tool, if the 'Limit the number of nearest locations to' is unchecked, the tool returns the error message, "Error unable to complete operation."

Workaround

Select the check box for 'Limit the number of nearest locations to' and input the desired value, or the default limit if the box is left unchecked, 100, as stated in the documentation: https://doc.arcgis.com/en/arcgis-online/analyze/find-nearest.htm

Steps to Reproduce