NSURLErrorNetworkUnavailableReasonConstrained
A reason that indicates network is unavailable because the user enabled “Low Data Mode” in the Settings app.
Declaration
NSURLErrorNetworkUnavailableReasonConstrainedDiscussion
This reason occurs when the following conditions are true:
The only available network is cellular.
The user has enabled “Low Data Mode” option in the Cellular Data Options section of the Settings app.
The URLSessionConfiguration property allowsConstrainedNetworkAccess is false.