In ArcGIS Online, opening a web map returns the following error:
Error: Basemap is not available. Displaying the default basemap instead.
The following are possible causes for this issue.
In addition, there are known issues in ArcGIS Online and Portal for ArcGIS caused by BUG-000099434, which is triggered when a web map is opened that references an unavailable basemap.
Try one of the following workarounds to solve this issue.
Note: Organizations can apply a domain filter to determine the domains that are allowed and restricted within the organization. Domain Requirements for ArcGIS Online provides a list of URLs which must be added into the organization's allowed list for ArcGIS Online to have full functionality.
Note: The ArcGIS Online Assistant can also be used to determine if mixed content is used by inspecting the web maps JSON. For more information, see ArcGIS Online: Troubleshoot.