Error:
Unable to load the base map layer (Unable to load //services.arcgisonline.com/ArcGIS/rest/services/World_Topo_Map/MapServer?f=json status: 0 [url:https://services.arcgisonline.com/ArcGIS/rest/services/World_Topo_Map/MapServer])
I can access both of the URLs you provide without any issues. Do you have a smart phone you can try the URLs on to see if it might be something with your local ISP connection?
Thank you, now they are all working again
It is also wise to check ArcGIS Online Health Dashboard to see if there is any problem reported. In this case no problems seem to be reported with the base maps.