Many organizations are interested in creating Open Data sites to allow the public to view and download data. To do this, they may use a distributed collaboration between ArcGIS Online and ArcGIS Enterprise to share content, and ArcGIS Hub to make the data publicly available. One issue that may come up during this process is an API error that displays when attempting to download a hosted feature layer from ArcGIS Hub. Related to this issue is the absence of the Export Data button in the Item Details page in ArcGIS Online.
This error is due to content shared through the distributed collaboration as references, instead of as copies. Editing the collaboration to share content as copies resolves the issue, but all items to be shared must be sync-enabled.
Note: This is not the only cause of API errors when attempting to download data from ArcGIS Hub.
The solution is to create a collaboration between ArcGIS Online and ArcGIS Enterprise that shares hosted feature layers as copies, not references.
After creating the collaboration, items in the group attached to the workspace in Portal are sent to the group attached to the workspace in ArcGIS Online. The items is then shared through the Content group to the Content Library of ArcGIS Hub. From ArcGIS Hub, hosted feature layers should be able to be downloaded successfully once the collaboration workspace has synced and the layers have been shared as copies.
You can also check by seeing if the Export Data option is available from the Item Details page of a feature layer in the Content group in ArcGIS Online.