I use that site also and just tried it. Looks like it is working ok. Maybe just a temporary internet glitch. They have been known to happen here and elsewhere....
I have used USGS maps to figure acreage. They may be more exact than the USDA maps. You can download them as PDF files and then with a free add-on you can calculate distance and area. You can also put them on a laptop and connect a GPS and they are supposed to show exactly where on the map you are located. The USGS maps come in traditional TOPO format or new DIGI format.