The following message is returned after uploading a zipped folder to Content in ArcGIS Online.
Error: Error Processing table data - check file format, supported data types and data license.
The file uploaded to ArcGIS Online is a higher-level folder that contains the file geodatabase folder, and is not directly the zipped file geodatabase itself.
The zipped folder name must be written in the format, [name].gdb.zip. In addition, the title in ArcGIS cannot contain special characters (such as ".gdb").