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.
As an Amazon Associate we earn from qualifying purchases. Product prices and availability are accurate as of the date/time indicated and are subject to change.