All network rules and access rules are configured using Identity Provider Discovery. Ensure your identity provider has on premises IWA Desktop SSO. See Configure identity provider routing rules.
If you turn off IWA DSSO, the IWA Routing Rule becomes Inactive and the next Routing Rule is used to direct users to the appropriate sign in. When you turn IWA DSSO on again, you must also switch the IWA Routing Rule to Active.