Issue uploading custom widget to Arcgis portal

[najeebhall]

Good day,

I am following the instructions found on Add Custom Widgets to Web AppBuilder for ArcGIS Developer Edition  and on https://www.esri.com/arcgis-blog/products/mapping/mapping/web-appbuilder-for-arcgis-now-supports-cus...  in order to upload a custom widget to my arcgis portal. I am am however receiving this error message and since it does not give any information I am not sure whats wrong. I have successfully imported the widget into my arcgis web app builder for developers and created an app and used the widget. Any thoughts on what could e causing this?