The download option is not available and the item type changes depending on how an item is searched using the ArcGIS Hub Open Data template with a map service from ArcGIS Server through a distributed collaboration.
Unable reproduce the specific defects with the provided example resources. Both the customer and in-house reproduction cases do not show the specified issues on either the search view or the content view. Test again to see if the specific issues persist. Contact the account managers on specific enhancement requests for ArcGIS Hub to support downloading directly from items that reference single-layer and multi-layer services. For more details on the roadmap, refer below.
Items that directly reference multi-layer services (including Feature Services and Map Services) or single-layer services will not show a download button, which is expected behavior. Select the service from search results, then select a layer to explore and then download. ArcGIS Hub does not support downloading all layers of a multi-layer service directly.
This issue has shifted to supporting downloading without requiring as many clicks or without visiting as many pages. It has been reverified that the workaround does work and users are to publish items that reference a layer from a single-layer or multi-layer map service, and then share that item to a ArcGIS Hub site catalog. Subsequently, when a user visits the search view, including the upcoming beta search view accessible at {siteURL}/explore) and selects an item, then they will view the item's content view. A download button is displayed.
The ArcGIS Hub team is planning ways to make it easier to download content with fewer clicks. Improvements include 1: the ability to download from the layers list on a multi-service's /about content view, 2. the ability to download directly from search results, 3. a download layout card.
解决办法
Add the map service directly to ArcGIS Online without a distributed collaboration using the Add Item option in ArcGIS Online.
Add the item to Portal for ArcGIS referencing the specific sublayer (for example, https://server/arcgis/rest/services/Title/MapServer/0).