We are experiencing ArcGIS Online service disruption. Please follow our status page for more details and for updates: https://status.nearmap.com.
Other than the ArcGIS Online service disruption, you may encounter the error described in this page. The solution is also described here.
Esri's ArcGIS Online have transitioned to utilizing TLS 1.2 only on April 16 2019, and some clients/versions will experience a disruption of service if they do not follow the steps described in Esri's TLS_Guidance.